feat(git): add ignore and untrack paths commands

The changes introduce server-side commands to manage gitignore
 rules and to untrack paths without deleting local files.
 A new GitIgnoreKind enum and helper functions normalize targets
 and build proper ignore patterns, and UI code was wired to use
 these commands.

- add_to_gitignore command and related helpers
- untrack_paths command to remove paths from the index
- UI wiring to expose ignore and untrack actions in explorer

src/lib/git.ts

@@ -14,6 +14,7 @@ import type {
   GitBranch,
   GitCommit,
   GitCommitComparison,
+  GitIgnoreKind,
   GitLfsStatus,
   GitRepositoryFile,
   GitRemote,
@@ -291,6 +292,14 @@ export function unstageFiles(path: string, files: string[]): Promise<GitStatus>
   return invoke<GitStatus>("unstage_files", { path, files });
 }
 
+export function addToGitignore(path: string, target: string, kind: GitIgnoreKind): Promise<GitStatus> {
+  return invoke<GitStatus>("add_to_gitignore", { path, target, kind });
+}
+
+export function untrackPaths(path: string, targets: string[]): Promise<GitStatus> {
+  return invoke<GitStatus>("untrack_paths", { path, targets });
+}
+
 export function restoreFiles(
   path: string,
   files: string[],