feat: add Files tab for browsing workspace files (#154)

* feat: add Files tab for browsing workspace files

- Add Files tab between Diff and Terminal in header
- Implement hierarchical file tree with expand/collapse
- Add fuzzy search with debouncing and relevance ranking
- Support gitignore filtering via `git check-ignore` (web + desktop)
- Add syntax highlighting for 150+ file types
- Add image preview (SVG, PNG, JPG, etc.)
- Add line numbers, wrap toggle, and copy button
- Desktop: split-pane layout matching DiffView
- Mobile: drill-in navigation with full-width sidebar
- Update help dialog with Cmd+3 shortcut
- Increase header breakpoint to 940px for new tab

* feat: enhance context and session stores to track agent/model/variant choices for historical sessions

* feat: implement line selection and commenting functionality in FilesView

packages/ui/src/stores/useSessionStore.ts

@@ -288,6 +288,24 @@ export const useSessionStore = create<SessionStore>()(
                         }
 
                         get().trimToViewportWindow(id, ACTIVE_SESSION_WINDOW);
+
+                        // Analyze session messages to extract agent/model/variant choices
+                        // This ensures context is available even when ModelControls isn't mounted
+                        const sessionMessages = get().messages.get(id);
+                        if (sessionMessages && sessionMessages.length > 0) {
+                            const agents = useConfigStore.getState().agents;
+                            if (agents.length > 0) {
+                                try {
+                                    await useContextStore.getState().analyzeAndSaveExternalSessionChoices(
+                                        id,
+                                        agents,
+                                        get().messages
+                                    );
+                                } catch (error) {
+                                    console.warn('Failed to analyze session choices:', error);
+                                }
+                            }
+                        }
                     }
 
                     get().evictLeastRecentlyUsed();