feat(clone): add repository cloning flow to UI and backend

This introduces a new Tauri command to clone a remote repository into a
validated destination folder, then return the full repository bundle for
immediate rendering. The Svelte app gains a clone dialog and a new action
in repository management, wiring the cloned bundle into existing refresh
helpers. Dialog backdrops were also adjusted to rely on explicit close
controls.

- Add clone_repository command and core cloning logic in Rust
- Create CloneRepositoryDialog and integrate it into App.svelte
- Improve clone-related styling and tighten dialog backdrop behavior

src/lib/components/CloneRepositoryDialog.svelte

@@ -0,0 +1,158 @@
+<script lang="ts">
+  import { open as openDialog } from "@tauri-apps/plugin-dialog";
+  import { Download, FolderOpen, LoaderCircle, X } from "@lucide/svelte";
+
+  interface Props {
+    isBusy: boolean;
+    error: string;
+    onClone: (remoteUrl: string, parentPath: string, directoryName: string) => void;
+    onClose: () => void;
+  }
+
+  let {
+    isBusy = false,
+    error = "",
+    onClone = () => {},
+    onClose = () => {},
+  }: Props = $props();
+
+  let remoteUrl = $state("");
+  let parentPath = $state("");
+  let directoryName = $state("");
+  let directoryNameEdited = $state(false);
+  let directoryAutoName = $state("");
+  let browseError = $state("");
+
+  let directorySuggestion = $derived(directoryNameFromRemoteUrl(remoteUrl));
+  let canSubmit = $derived(
+    !isBusy &&
+    remoteUrl.trim().length > 0 &&
+    parentPath.trim().length > 0,
+  );
+  let visibleError = $derived(error || browseError);
+
+  function directoryNameFromRemoteUrl(url: string): string {
+    const trimmed = url.trim().split(/[?#]/, 1)[0]?.replace(/[\\/]+$/g, "") ?? "";
+    const lastSegment = trimmed.split(/[\\/:]/).filter(Boolean).pop() ?? "";
+    return lastSegment.replace(/\.git$/i, "").trim();
+  }
+
+  function errorToMessage(error: unknown): string {
+    if (error instanceof Error) return error.message;
+    if (typeof error === "string") return error;
+    try { return JSON.stringify(error) ?? "Unknown error"; } catch { return "Unknown error"; }
+  }
+
+  async function chooseParentFolder() {
+    if (isBusy) return;
+    browseError = "";
+    try {
+      const selected = await openDialog({
+        title: "Select clone destination",
+        directory: true,
+        multiple: false,
+        defaultPath: parentPath.trim() || undefined,
+      });
+      if (typeof selected !== "string") return;
+      parentPath = selected;
+    } catch (error) {
+      browseError = errorToMessage(error);
+    }
+  }
+
+  function handleRemoteInput(event: Event) {
+    const nextRemoteUrl = (event.currentTarget as HTMLInputElement).value;
+    if (directoryNameEdited) return;
+    directoryAutoName = directoryNameFromRemoteUrl(nextRemoteUrl);
+    directoryName = directoryAutoName;
+  }
+
+  function handleDirectoryInput(event: Event) {
+    const nextDirectoryName = (event.currentTarget as HTMLInputElement).value;
+    directoryNameEdited = nextDirectoryName.trim().length > 0 && nextDirectoryName !== directoryAutoName;
+  }
+
+  function submit(event: SubmitEvent) {
+    event.preventDefault();
+    if (!canSubmit) return;
+    onClone(remoteUrl.trim(), parentPath.trim(), directoryName.trim());
+  }
+
+</script>
+
+<div class="dialog-backdrop" role="presentation">
+  <div class="dialog clone-repository-dialog" role="dialog" aria-modal="true" aria-label="Clone repository" tabindex="-1">
+    <header class="dialog-header">
+      <div>
+        <span class="eyebrow">Repository Management</span>
+        <h2 class="mt-0.5 text-ink text-base font-bold leading-tight">Clone repository</h2>
+      </div>
+      <button class="dialog-close" type="button" onclick={onClose} disabled={isBusy} title="Close">
+        <X size={18} aria-hidden="true" />
+      </button>
+    </header>
+
+    <form class="clone-dialog-form" onsubmit={submit}>
+      <label class="clone-dialog-field">
+        <span>Remote URL</span>
+        <!-- svelte-ignore a11y_autofocus -->
+        <input
+          bind:value={remoteUrl}
+          oninput={handleRemoteInput}
+          autocomplete="off"
+          spellcheck="false"
+          placeholder="https://github.com/org/project.git"
+          disabled={isBusy}
+          autofocus
+        />
+      </label>
+
+      <label class="clone-dialog-field">
+        <span>Destination</span>
+        <div class="clone-dialog-path-field">
+          <input
+            bind:value={parentPath}
+            autocomplete="off"
+            spellcheck="false"
+            placeholder="Choose parent folder"
+            disabled={isBusy}
+          />
+          <button class="btn-secondary" type="button" onclick={chooseParentFolder} disabled={isBusy}>
+            <FolderOpen size={14} aria-hidden="true" />
+            Browse
+          </button>
+        </div>
+      </label>
+
+      <label class="clone-dialog-field">
+        <span>Folder name</span>
+        <input
+          bind:value={directoryName}
+          oninput={handleDirectoryInput}
+          autocomplete="off"
+          spellcheck="false"
+          placeholder={directorySuggestion || "Optional"}
+          disabled={isBusy}
+        />
+      </label>
+
+      {#if visibleError}
+        <div class="clone-dialog-error" role="alert">{visibleError}</div>
+      {/if}
+
+      <div class="clone-dialog-actions">
+        <button class="btn-secondary" type="button" onclick={onClose} disabled={isBusy}>
+          Cancel
+        </button>
+        <button class="btn-primary" type="submit" disabled={!canSubmit}>
+          {#if isBusy}
+            <LoaderCircle class="spin" size={16} aria-hidden="true" />
+          {:else}
+            <Download size={16} aria-hidden="true" />
+          {/if}
+          Clone
+        </button>
+      </div>
+    </form>
+  </div>
+</div>