Implement interactive hunk staging and discarding

Introduce a new dialog that allows users to view file changes as individual hunks and selectively stage, unstage, or discard them. This provides more granular control over modifications, similar to `git add -p`.

Enhance branch panel usability by allowing double-click to checkout a branch.

src/lib/git.ts

@@ -8,6 +8,7 @@ import type {
   GitRepositoryFile,
   GitSearchHit,
   GitStatus,
+  PatchApplyAction,
   RepositoryBundle,
   StoredCredential,
 } from "./types";
@@ -56,6 +57,19 @@ export function restoreFiles(
   return invoke<GitStatus>("restore_files", { path, files, staged });
 }
 
+export function getFilePatch(path: string, file: string, staged: boolean): Promise<string> {
+  return invoke<string>("get_file_patch", { path, file, staged });
+}
+
+export function applyFilePatch(
+  path: string,
+  file: string,
+  patch: string,
+  action: PatchApplyAction,
+): Promise<GitStatus> {
+  return invoke<GitStatus>("apply_file_patch", { path, file, patch, action });
+}
+
 export function commit(path: string, message: string): Promise<GitStatus> {
   return invoke<GitStatus>("commit", { path, message });
 }