feat(app): replace add memory dialog with full-screen TipTap editor

- Add new TipTap-based NoteEditor component with formatting toolbar
- Add EditorContent, EditorToolbar, EditorActionBar components
- Add useSave hook for save state management
- Remove AddMemoryDialog in favor of full-screen editing
- Update MemoryDetailPanel to open editor for notes
- Add TipTap prose styling and editor design tokens
- Add FTS5 graceful fallback migration

Closes #55

Author: Antonio Maiolo

.changeset/full-screen-note-editor.md

@@ -0,0 +1,9 @@
+---
+"think-app": patch
+---
+
+Replace add memory dialog with full-screen TipTap editor
+
+- Add new TipTap-based NoteEditor component with formatting toolbar
+- Remove AddMemoryDialog in favor of full-screen editing experience
+- Update MemoryDetailPanel to open editor for notes

app/package.json

@@ -59,6 +59,10 @@
   },
   "dependencies": {
     "@microsoft/fetch-event-source": "^2.0.1",
+    "@tiptap/extension-placeholder": "^3.13.0",
+    "@tiptap/pm": "^3.13.0",
+    "@tiptap/react": "^3.13.0",
+    "@tiptap/starter-kit": "^3.13.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "lucide-react": "^0.460.0",