feat(git): Add comprehensive worktree management capabilities

This update introduces full support for Git worktrees, allowing users to manage multiple isolated working copies within a single repository. This includes new functionality to list, add, remove, move, lock, and repair worktrees, significantly enhancing the repository's capability to handle parallel development streams.

- Added `GitWorktree` structure definition across API contracts and Rust backend
- Implemented full CRUD operations for worktrees in Tauri commands
- Updated UI components (App.svelte, BranchPanel.svelte) to expose worktree management dialog

docs/api-contract.md

@@ -33,6 +33,24 @@ interface GitBranch {
   remote: boolean;
 }
 
+interface GitWorktree {
+  path: string;
+  head: string | null;
+  short_head: string | null;
+  branch: string | null;
+  bare: boolean;
+  detached: boolean;
+  locked: boolean;
+  lock_reason: string | null;
+  prunable: boolean;
+  prune_reason: string | null;
+  missing: boolean;
+  is_main: boolean;
+  is_current: boolean;
+  clean: boolean;
+  changed_files: number;
+}
+
 interface GitCommit {
   hash: string;
   short_hash: string;
@@ -73,6 +91,14 @@ The command list below includes the repository-management and synchronization AP
 - `set_branch_upstream(path: string, branch: string, upstream?: string): Promise<GitStatus>`
 - `delete_remote_branch(path: string, remote: string, branch: string): Promise<GitStatus>`
 - `checkout_branch(path: string, branch: string): Promise<GitStatus>`
+- `list_worktrees(path: string): Promise<GitWorktree[]>`
+- `add_worktree(path: string, worktreePath: string, ...): Promise<GitWorktree[]>`
+- `remove_worktree(path: string, worktreePath: string, force?: boolean): Promise<GitWorktree[]>`
+- `move_worktree(path: string, worktreePath: string, destination: string): Promise<GitWorktree[]>`
+- `lock_worktree(path: string, worktreePath: string, reason?: string): Promise<GitWorktree[]>`
+- `unlock_worktree(path: string, worktreePath: string): Promise<GitWorktree[]>`
+- `prune_worktrees(path: string): Promise<GitWorktree[]>`
+- `repair_worktree(path: string, worktreePath: string): Promise<GitWorktree[]>`
 - `stage_files(path: string, files: string[]): Promise<GitStatus>`
 - `unstage_files(path: string, files: string[]): Promise<GitStatus>`
 - `restore_files(path: string, files: string[], staged: boolean): Promise<GitStatus>`