feat(git): add ignore and untrack paths commands

The changes introduce server-side commands to manage gitignore
 rules and to untrack paths without deleting local files.
 A new GitIgnoreKind enum and helper functions normalize targets
 and build proper ignore patterns, and UI code was wired to use
 these commands.

- add_to_gitignore command and related helpers
- untrack_paths command to remove paths from the index
- UI wiring to expose ignore and untrack actions in explorer

src/App.svelte

@@ -36,6 +36,7 @@
   import UpdateToast from "./lib/components/UpdateToast.svelte";
 
   import {
+    addToGitignore,
     amendCommit,
     addRemote,
     addWorktree,
@@ -137,6 +138,7 @@
     undoLastCommit,
     unlockWorktree,
     untrackGitLfsPattern,
+    untrackPaths,
     unstageFiles,
   } from "./lib/git";
 
@@ -161,6 +163,7 @@
     GitCommitComparison,
     GitDiffFile,
     GitFileStatus,
+    GitIgnoreKind,
     GitLfsStatus,
     GitRepositoryFile,
     GitRemote,
@@ -3947,6 +3950,25 @@
     });
   }
 
+  async function ignoreStatusTarget(target: string, kind: GitIgnoreKind) {
+    if (!activeRepoPath || !target) return;
+    const description = kind === "folder" ? "folder" : kind === "extension" ? "file extension" : "file";
+    await runOperation(`Ignoring ${description}`, async () => {
+      applyStatus(await addToGitignore(activeRepoPath, target, kind));
+      await refreshExplorerFiles(activeRepoPath);
+      trackEvent("gitignore_rule_added", { kind });
+    });
+  }
+
+  async function stopTrackingTarget(target: string, kind: "file" | "folder") {
+    if (!activeRepoPath || !target) return;
+    await runOperation(`Stopping tracking for ${kind}`, async () => {
+      applyStatus(await untrackPaths(activeRepoPath, [target]));
+      await refreshExplorerFiles(activeRepoPath);
+      trackEvent("git_paths_untracked", { kind });
+    });
+  }
+
   function discardFiles(files: GitFileStatus[], staged: boolean) {
     if (!activeRepoPath || isBusy || files.length === 0) return;
     pendingDiscard = { kind: "file", files, staged };
@@ -5309,6 +5331,8 @@
           onExternalDiff={compareExplorerFileExternally}
           onFileHistory={openFileHistoryDialog}
           onBlame={openBlame}
+          onIgnore={ignoreStatusTarget}
+          onStopTracking={stopTrackingTarget}
           collapsed={explorerPanelCollapsed}
           onToggleCollapsed={toggleExplorerPanelCollapsed}
         />
@@ -5378,6 +5402,8 @@
             onDiscard={discardFiles}
             onDiscardMany={discardChanges}
             onStash={stashStatusFiles}
+            onIgnore={ignoreStatusTarget}
+            onStopTracking={stopTrackingTarget}
             onPatch={openPreferredFileDiff}
             onStageAll={stageAllFiles}
             onUnstageAll={unstageAllFiles}