feat(git): add rebase workflow with UI state handling

This introduces Git rebase commands (start, continue, abort) and
exposes whether a rebase is currently in progress via the status
payload. The UI now blocks committing during an active rebase and
shows a dedicated rebase notice with continue/abort actions.

- Add tauri commands for rebase operations and status detection
- Update frontend to render rebase state and controls
- Adjust conflict/resolution messaging and related UI styling

src/lib/git.ts

@@ -219,6 +219,18 @@ export function mergeBranch(path: string, branch: string): Promise<GitStatus> {
   return invoke<GitStatus>("merge_branch", { path, branch });
 }
 
+export function rebaseBranch(path: string, branch: string): Promise<GitStatus> {
+  return invoke<GitStatus>("rebase_branch", { path, branch });
+}
+
+export function rebaseContinue(path: string): Promise<GitStatus> {
+  return invoke<GitStatus>("rebase_continue", { path });
+}
+
+export function rebaseAbort(path: string): Promise<GitStatus> {
+  return invoke<GitStatus>("rebase_abort", { path });
+}
+
 export function listRepositoryFiles(path: string): Promise<GitRepositoryFile[]> {
   return invoke<GitRepositoryFile[]>("list_repository_files", { path });
 }