feat(git): add commit-note support and previews in history

This change adds Git notes support to the history UI.
Commits now carry a has_note flag which triggers a note indicator.
Notes can be previewed on hover and loaded on demand,
then the history can be refreshed after edits.

- Adds has_note support on commits and parses from logs.
- Renders a note indicator in history rows with a hover preview.
- Triggers history refresh after note-related actions.

src/lib/types.ts

@@ -178,6 +178,7 @@ export interface GitCommit {
   refs: string[];
   parents: string[];
   files: GitCommitFile[];
+  has_note: boolean;
 }
 
 export interface GitCommitFile {