feat(tui): wire entity cache for near-instant detail view reopens (bd-3rjw)

- Add get_mut() and clear() methods to EntityCache<V>
- Add CachedIssuePayload / CachedMrPayload types to state
- Wire cache check in navigate_to for instant cache hits
- Populate cache on IssueDetailLoaded / MrDetailLoaded
- Update cache on DiscussionsLoaded
- Add 6 new entity_cache tests (get_mut, clear)

crates/lore-tui/src/view/search.rs

@@ -102,7 +102,15 @@ pub fn render_search(frame: &mut Frame<'_>, state: &SearchState, area: Rect) {
     if state.results.is_empty() {
         render_empty_state(frame, state, area.x + 1, y, max_x);
     } else {
-        render_result_list(frame, state, area.x, y, area.width, list_height, show_project);
+        render_result_list(
+            frame,
+            state,
+            area.x,
+            y,
+            area.width,
+            list_height,
+            show_project,
+        );
     }
 
     // -- Bottom hint bar -----------------------------------------------------