feat(ui): localize commit AI and git error messages to English

Translate commit AI prompts, model labels, and git/keychain errors to
English so the app and generated messages are consistent. Also add a
discard confirmation dialog and update the UI text/styles to match the
new flow.

- src-tauri/crates/commit_ai/src/cloud.rs
  - Translate HTTP and API error messages to English.
  - Keep request timeout and token sizing behavior unchanged.
- src-tauri/crates/commit_ai/src/lib.rs
  - Translate model labels, prompt text, and validation errors.
  - Keep diff truncation and message sanitization logic intact.
- src-tauri/src/git.rs
  - Translate git, credential, merge, and history errors.
  - Update AI provider validation messages to English.
- src/lib/components/*
  - Update AI settings, commit panel, credential, and loading UI text.
  - Add discard confirmation dialog for destructive actions.
- src/App.svelte, src/app.css
  - Adjust app layout and styling for the new dialog and text changes.

src/App.svelte

@@ -11,6 +11,7 @@
   import CompareDialog from "./lib/components/CompareDialog.svelte";
   import CompareSelectDialog from "./lib/components/CompareSelectDialog.svelte";
   import CredentialDialog from "./lib/components/CredentialDialog.svelte";
+  import DiscardConfirmDialog from "./lib/components/DiscardConfirmDialog.svelte";
   import ExplorerPanel from "./lib/components/ExplorerPanel.svelte";
   import FileHistoryPanel from "./lib/components/FileHistoryPanel.svelte";
   import GlobalSearchDialog from "./lib/components/GlobalSearchDialog.svelte";
@@ -96,6 +97,9 @@
 
   type UpdateToastState = "available" | "downloading" | "installed" | "error";
   type AppView = "management" | "repository";
+  type PendingDiscard =
+    | { kind: "file"; file: GitFileStatus; staged: boolean }
+    | { kind: "hunk"; file: GitFileStatus; staged: boolean; action: PatchApplyAction; patch: string };
 
   interface RepoTab {
     path: string;
@@ -110,6 +114,10 @@
   const OPEN_REPOS_KEY = "gitlite.openRepos.v1";
   const RECENT_REPOS_KEY = "gitlite.recentRepos.v1";
   const AI_SETTINGS_KEY = "gitlite.aiSettings.v1";
+  const COMMIT_PANEL_HEIGHT_KEY = "gitlite.commitPanelHeight.v1";
+  const COMMIT_PANEL_DEFAULT_HEIGHT = 220;
+  const COMMIT_PANEL_MIN_HEIGHT = COMMIT_PANEL_DEFAULT_HEIGHT;
+  const COMMIT_PANEL_MAX_HEIGHT = 640;
 
   // ── State ──────────────────────────────────────────────────────────────────
 
@@ -157,6 +165,7 @@
   let linePatchText = "";
   let linePatchLoading = false;
   let linePatchError = "";
+  let pendingDiscard: PendingDiscard | null = null;
   let globalSearchOpen = false;
   let lastSearchQuery = "";
   let globalSearchResults: GitSearchHit[] = [];
@@ -186,6 +195,10 @@
   let updateCheckInFlight = false;
   let updateDownloadTotal = 0;
   let updateDownloadedBytes = 0;
+  let commitPanelHeight = loadCommitPanelHeight();
+  let resizingCommitPanel = false;
+  let resizeStartY = 0;
+  let resizeStartHeight = 0;
 
   // ── Derived ────────────────────────────────────────────────────────────────
 
@@ -542,6 +555,56 @@
     }
   }
 
+  function clampCommitPanelHeight(value: number): number {
+    return Math.min(COMMIT_PANEL_MAX_HEIGHT, Math.max(COMMIT_PANEL_MIN_HEIGHT, Math.round(value)));
+  }
+
+  function loadCommitPanelHeight(): number {
+    try {
+      const stored = Number(localStorage.getItem(COMMIT_PANEL_HEIGHT_KEY));
+      if (Number.isFinite(stored) && stored > 0) return clampCommitPanelHeight(stored);
+    } catch {
+      // Fall through to the default below.
+    }
+    return COMMIT_PANEL_DEFAULT_HEIGHT;
+  }
+
+  function persistCommitPanelHeight(value: number) {
+    try {
+      localStorage.setItem(COMMIT_PANEL_HEIGHT_KEY, String(value));
+    } catch {
+      // Local storage is best-effort only; resizing must keep working without it.
+    }
+  }
+
+  function startCommitPanelResize(event: PointerEvent) {
+    event.preventDefault();
+    resizingCommitPanel = true;
+    resizeStartY = event.clientY;
+    resizeStartHeight = commitPanelHeight;
+    (event.currentTarget as HTMLElement).setPointerCapture(event.pointerId);
+  }
+
+  function onCommitPanelResizeMove(event: PointerEvent) {
+    if (!resizingCommitPanel) return;
+    commitPanelHeight = clampCommitPanelHeight(resizeStartHeight + (resizeStartY - event.clientY));
+  }
+
+  function endCommitPanelResize(event: PointerEvent) {
+    if (!resizingCommitPanel) return;
+    resizingCommitPanel = false;
+    persistCommitPanelHeight(commitPanelHeight);
+    const target = event.currentTarget as HTMLElement;
+    if (target.hasPointerCapture(event.pointerId)) target.releasePointerCapture(event.pointerId);
+  }
+
+  function onCommitPanelResizeKeydown(event: KeyboardEvent) {
+    if (event.key !== "ArrowUp" && event.key !== "ArrowDown") return;
+    event.preventDefault();
+    commitPanelHeight = clampCommitPanelHeight(commitPanelHeight + (event.key === "ArrowUp" ? 20 : -20));
+    persistCommitPanelHeight(commitPanelHeight);
+  }
+
   function rememberRecentRepo(path: string) {
     recentRepoPaths = uniqueRepoPaths([path, ...recentRepoPaths]).slice(0, 40);
     persistRepoLists();
@@ -692,7 +755,7 @@
   }
 
   function isCancellationMessage(message: string): boolean {
-    return message.toLowerCase().includes("abgebrochen");
+    return message.toLowerCase().includes("cancelled");
   }
 
   function cancelActiveFileHistoryLoad() {
@@ -766,7 +829,7 @@
     if (isBusy) return;
     try {
       const selected = await openDialog({
-        title: "Repository folder auswaehlen",
+        title: "Select repository folder",
         directory: true,
         multiple: false,
         defaultPath: repoPath.trim() || activeRepoPath || undefined,
@@ -975,7 +1038,7 @@
       if (auth) {
         if (key) void credDelete(key).catch(() => {});
         credDialogError =
-          "Zugangsdaten wurden abgelehnt oder sind abgelaufen. Bitte erneut anmelden.";
+          "Credentials were rejected or have expired. Please sign in again.";
         credDialogAction = action;
         credDialogKey = key;
         credDialogOpen = true;
@@ -984,7 +1047,7 @@
         errorMessage = message;
       }
     } else {
-      credDialogError = message || "Anmeldung fehlgeschlagen.";
+      credDialogError = message || "Sign-in failed.";
     }
   }
 
@@ -1022,11 +1085,11 @@
     if (errorMessage && !isAuthError(errorMessage) && isNonFastForwardPushError(errorMessage)) {
       errorMessage = "";
       const shouldSync = window.confirm(
-        "Der Remote hat neuere Commits, deshalb wurde der Push abgelehnt.\n\nJetzt Pull/Merge ausfuehren und danach den Push erneut versuchen?",
+        "The remote has newer commits, so the push was rejected.\n\nRun Pull/Merge now and try pushing again afterwards?",
       );
 
       if (!shouldSync) {
-        const message = "Push abgelehnt: Der Remote hat neuere Commits. Pull zuerst ausfuehren, dann erneut pushen.";
+        const message = "Push rejected: the remote has newer commits. Pull first, then push again.";
         if (fromStore) errorMessage = message;
         else credDialogError = message;
         return;
@@ -1050,7 +1113,7 @@
       if (statusHasConflicts(status)) {
         credDialogOpen = false;
         credDialogAction = null;
-        errorMessage = "Pull hat Merge-Konflikte erzeugt. Loese die Konflikte, committe den Merge und pushe danach erneut.";
+        errorMessage = "Pull produced merge conflicts. Resolve the conflicts, commit the merge, and then push again.";
         return;
       }
 
@@ -1125,7 +1188,12 @@
     });
   }
 
-  async function discardFile(file: GitFileStatus, staged: boolean) {
+  function discardFile(file: GitFileStatus, staged: boolean) {
+    if (!activeRepoPath || isBusy) return;
+    pendingDiscard = { kind: "file", file, staged };
+  }
+
+  async function runDiscardFile(file: GitFileStatus, staged: boolean) {
     await runOperation(`Discarding ${file.path}`, async () => {
       applyStatus(await restoreFiles(activeRepoPath, [file.path], staged));
       await refreshExplorerFiles(activeRepoPath);
@@ -1176,9 +1244,17 @@
     }
   }
 
-  async function applyLinePatch(action: PatchApplyAction, patch: string) {
-    if (!activeRepoPath || !linePatchFile || isBusy) return;
-    const file = linePatchFile;
+  function isDiscardPatchAction(action: PatchApplyAction): boolean {
+    return action === "discard-staged" || action === "discard-unstaged";
+  }
+
+  async function runLinePatchAction(
+    action: PatchApplyAction,
+    patch: string,
+    file: GitFileStatus,
+    staged: boolean,
+  ) {
+    if (!activeRepoPath || isBusy) return;
     operation = patchOperationLabel(action, file);
     errorMessage = "";
     linePatchError = "";
@@ -1188,7 +1264,7 @@
       await refreshExplorerFiles(activeRepoPath);
       await refreshFileHistory(activeRepoPath);
 
-      const updatedPatch = await getFilePatch(activeRepoPath, file.path, linePatchStaged);
+      const updatedPatch = await getFilePatch(activeRepoPath, file.path, staged);
       if (updatedPatch.trim()) {
         linePatchText = updatedPatch;
       } else {
@@ -1204,6 +1280,37 @@
     }
   }
 
+  async function applyLinePatch(action: PatchApplyAction, patch: string) {
+    if (!activeRepoPath || !linePatchFile || isBusy) return;
+    const file = linePatchFile;
+    const staged = linePatchStaged;
+
+    if (isDiscardPatchAction(action)) {
+      pendingDiscard = { kind: "hunk", file, staged, action, patch };
+      return;
+    }
+
+    await runLinePatchAction(action, patch, file, staged);
+  }
+
+  async function confirmDiscard() {
+    const discard = pendingDiscard;
+    if (!discard || !activeRepoPath || isBusy) return;
+
+    if (discard.kind === "file") {
+      await runDiscardFile(discard.file, discard.staged);
+    } else {
+      await runLinePatchAction(discard.action, discard.patch, discard.file, discard.staged);
+    }
+
+    pendingDiscard = null;
+  }
+
+  function closeDiscardConfirm() {
+    if (isBusy) return;
+    pendingDiscard = null;
+  }
+
   async function stageAllFiles() {
     const paths = changedFiles.filter((f) => f.unstaged !== null).map((f) => f.path);
     if (paths.length === 0) return;
@@ -1441,7 +1548,7 @@
     } catch (error) {
       if (globalSearchId === searchId) {
         const message = errorToMessage(error);
-        globalSearchError = message.includes("abgebrochen") ? "Suche wurde abgebrochen." : message;
+        globalSearchError = message.includes("cancelled") ? "Search was cancelled." : message;
       }
     } finally {
       if (globalSearchId === searchId) {
@@ -1454,7 +1561,7 @@
   async function cancelGlobalSearch() {
     if (!globalSearchId) return;
     const searchId = globalSearchId;
-    globalSearchError = "Abbruch wird angefordert...";
+    globalSearchError = "Requesting cancellation...";
     try {
       await cancelCodeSearch(searchId);
     } catch (error) {
@@ -1533,7 +1640,8 @@
   // ── Event handlers ─────────────────────────────────────────────────────────
 
   function handleWindowKeydown(event: KeyboardEvent) {
-    if (event.key === "Escape" && compareDialogOpen) closeCompareDialog();
+    if (event.key === "Escape" && pendingDiscard && !isBusy) closeDiscardConfirm();
+    else if (event.key === "Escape" && compareDialogOpen) closeCompareDialog();
     else if (event.key === "Escape" && newBranchCommit) newBranchCommit = null;
     else if (event.key === "Escape" && renameBranchTarget) renameBranchTarget = null;
     else if (event.key === "Escape" && compareSelectOpen) compareSelectOpen = false;
@@ -1813,7 +1921,7 @@
           </div>
         </div>
 
-        <div class="top-section">
+        <div class="top-section" style="--commit-panel-height: {commitPanelHeight}px;">
           <StatusPanel
             {changedFiles}
             {stagedCount}
@@ -1830,6 +1938,24 @@
             onStageAll={stageAllFiles}
             onUnstageAll={unstageAllFiles}
           />
+          <!-- svelte-ignore a11y_no_noninteractive_tabindex -->
+          <!-- svelte-ignore a11y_no_noninteractive_element_interactions -->
+          <div
+            class="panel-resize-handle"
+            class:resizing={resizingCommitPanel}
+            role="separator"
+            aria-orientation="horizontal"
+            aria-label="Resize commit panel height"
+            aria-valuenow={commitPanelHeight}
+            aria-valuemin={COMMIT_PANEL_MIN_HEIGHT}
+            aria-valuemax={COMMIT_PANEL_MAX_HEIGHT}
+            tabindex="0"
+            onpointerdown={startCommitPanelResize}
+            onpointermove={onCommitPanelResizeMove}
+            onpointerup={endCommitPanelResize}
+            onpointercancel={endCommitPanelResize}
+            onkeydown={onCommitPanelResizeKeydown}
+          ></div>
           <CommitPanel
             {commitMessage}
             {canCommit}
@@ -1908,6 +2034,17 @@
   />
 {/if}
 
+{#if pendingDiscard}
+  <DiscardConfirmDialog
+    file={pendingDiscard.file}
+    staged={pendingDiscard.staged}
+    scope={pendingDiscard.kind === "hunk" ? "hunk" : "file"}
+    {isBusy}
+    onConfirm={confirmDiscard}
+    onClose={closeDiscardConfirm}
+  />
+{/if}
+
 {#if globalSearchOpen}
   <GlobalSearchDialog
     {hasRepository}