feat: codebase mapper with CODEBASE.md generation (#190)

- Add scan_project Rust command that walks the directory tree and detects project type
- Add CODEBASE as a managed ProjectFile type alongside PROJECT/REQUIREMENTS/ROADMAP/STATE
- Add mapCodebase() store function that scans and sends an analysis prompt to Claude
- Add CODEBASE tab to ProjectContextPanel with Map/Remap buttons and auto-reload on idle
- Update PROJECT_CONTEXT_SYSTEM_ADDENDUM to include CODEBASE.md reference

src-tauri/src/lib.rs

@@ -220,6 +220,7 @@ pub fn run() {
             save_draft,
             delete_draft,
             delete_all_drafts,
+            scan_project,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");