Optimize repository loading and enhance Git UI

Consolidate multiple Git backend calls into a single bundle to reduce
overhead when opening and auto-refreshing repositories. This significantly
improves performance by fetching status, branches, commits, and files
in one optimized operation, instead of re-running 'git rev-parse' and
'git status' multiple times.

Also, streamline commit history loading by fetching file changes inline
via 'git log --name-status -z', eliminating expensive per-commit
'git diff-tree' processes.

Additionally, introduce the ability to create new branches from a
specific commit in the history and refactor the commit comparison
feature into a dedicated dialog. The status panel now displays concise
file names.

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, LoaderCircle, Minus, RefreshCw, Search, Upload, X } from "@lucide/svelte";
+  import { Download, GitBranch, GitCompare, LoaderCircle, Minus, RefreshCw, Search, Upload, X } from "@lucide/svelte";
 
   export let branch: string = "";
   export let ahead: number = 0;
@@ -16,6 +16,7 @@
   export let onPush: () => void = () => {};
   export let onRefresh: () => void = () => {};
   export let onSearch: () => void = () => {};
+  export let onCompare: () => void = () => {};
   export let onToggleAutoRefresh: () => void = () => {};
 
   const win = getCurrentWindow();
@@ -92,6 +93,17 @@
         <span class="tb-action-label">Search</span>
       </button>
 
+      <button
+        class="tb-action"
+        onclick={onCompare}
+        disabled={!hasRepository || isBusy}
+        title="Compare commits"
+        aria-label="Compare commits"
+      >
+        <GitCompare size={14} aria-hidden="true" />
+        <span class="tb-action-label">Compare</span>
+      </button>
+
       <button
         class="tb-action"
         onclick={onPull}