Implement repository management view and multi-repo tabs

Introduces a new "Repository Management" view for browsing open and recent repositories. Adds a tabbed interface for quickly switching between multiple active repositories, with persistent state. Also includes a new command to open the current repository in the native file explorer.

src/lib/TitleBar.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import { onDestroy, onMount } from "svelte";
   import { getCurrentWindow } from "@tauri-apps/api/window";
-  import { Download, GitBranch, GitCompare, LoaderCircle, Minus, RefreshCw, Search, Upload, X } from "@lucide/svelte";
+  import { Download, FolderOpen, GitBranch, GitCompare, LoaderCircle, Minus, RefreshCw, Search, Upload, X } from "@lucide/svelte";
 
   export let branch: string = "";
   export let ahead: number = 0;
@@ -17,6 +17,7 @@
   export let onRefresh: () => void = () => {};
   export let onSearch: () => void = () => {};
   export let onCompare: () => void = () => {};
+  export let onOpenInExplorer: () => void = () => {};
   export let onToggleAutoRefresh: () => void = () => {};
 
   const win = getCurrentWindow();
@@ -82,6 +83,17 @@
   <!-- Right: actions + window controls -->
   <div class="titlebar-right">
     <div class="titlebar-actions" role="toolbar" aria-label="Repository actions">
+      <button
+        class="tb-action"
+        onclick={onOpenInExplorer}
+        disabled={!hasRepository || isBusy}
+        title="Open repository in Explorer"
+        aria-label="Open repository in Explorer"
+      >
+        <FolderOpen size={14} aria-hidden="true" />
+        <span class="tb-action-label">Explorer</span>
+      </button>
+
       <button
         class="tb-action"
         onclick={onSearch}