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/components/HistoryPanel.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { ChevronDown, ChevronRight, RotateCcw } from "@lucide/svelte";
+  import { ChevronDown, ChevronRight, GitBranch, RotateCcw } from "@lucide/svelte";
   import type { FileStatusKind, GitCommit, GitCommitFile } from "../types";
 
   interface GraphSegment {
@@ -29,6 +29,7 @@
     onRestoreCommit: (commit: GitCommit) => void;
     onPreviewCommitFile: (commit: GitCommit, file: GitCommitFile) => void;
     onToggleCommitFiles: (hash: string) => void;
+    onCreateBranchFromCommit: (commit: GitCommit) => void;
   }
 
   let {
@@ -39,6 +40,7 @@
     onRestoreCommit = () => {},
     onPreviewCommitFile = () => {},
     onToggleCommitFiles = () => {},
+    onCreateBranchFromCommit = () => {},
   }: Props = $props();
 
   function laneColor(col: number): string {
@@ -220,6 +222,10 @@
             <div class="commit-actions">
               <time datetime={item.date}>{formatCommitDate(item.date)}</time>
               <div class="commit-action-buttons">
+                <button class="btn-sm" type="button" onclick={() => onCreateBranchFromCommit(item)} disabled={isBusy} title="Create a new branch from this commit">
+                  <GitBranch size={15} aria-hidden="true" />
+                  Branch
+                </button>
                 <button class="btn-sm" type="button" onclick={() => onRestoreCommit(item)} disabled={isBusy} title="Reset current branch to this commit">
                   <RotateCcw size={15} aria-hidden="true" />
                   Restore