UI polish pass: word count, slash commands, task lists, graph peek, bulk delete, export

- WordCount component (toggle words/chars vs read time, persisted mode)
- TipTap: TaskList/TaskItem extensions, slash command menu (H1-H3, lists, code, quote, task)
- Markdown serializer: task list → `- [ ]` / `- [x]` roundtrip
- GraphView: slide-in peek panel for note/task nodes (body, tags, linked nodes); tag nodes still navigate
- ChatView: bulk-select conversations with two-click confirm delete + chat retention policy (default 90d)
- NoteEditorView: pill tab bar with animated edit/preview toggle + WordCount in toolbar
- WorkspaceNoteEditor: inline search with tag matching, inline new-note creation, WordCount
- WorkspaceTaskPanel: task body rendered in slide-over + Edit link
- Settings: data export (Markdown ZIP / JSON) via GET /api/export
- Accessibility: skip-to-content link, aria-labels on all icon-only buttons
- Fix: export route used non-existent fabledassistant.database — corrected to async_session()
- Fix: ToolCallRecord.status type now includes "running" (was causing TS build error)
- Dockerfile: upgrade npm to latest before install to suppress major-version notice
- npm audit fix: patched minimatch (ReDoS) and rollup (path traversal) — 0 vulnerabilities

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/assets/prose.css

@@ -144,6 +144,42 @@
   text-decoration: none;
 }
 
+/* Task list */
+.prose ul[data-type="taskList"] {
+  list-style: none;
+  padding-left: 0.25rem;
+}
+
+.prose ul[data-type="taskList"] li {
+  display: flex;
+  align-items: baseline;
+  gap: 0.5rem;
+  margin-bottom: 0.2rem;
+}
+
+.prose ul[data-type="taskList"] li > label {
+  flex-shrink: 0;
+  user-select: none;
+  line-height: 1.6;
+}
+
+.prose ul[data-type="taskList"] li > label input[type="checkbox"] {
+  cursor: pointer;
+  accent-color: var(--color-primary);
+  width: 0.95em;
+  height: 0.95em;
+  margin: 0;
+}
+
+.prose ul[data-type="taskList"] li > div {
+  flex: 1;
+}
+
+.prose ul[data-type="taskList"] li[data-checked="true"] > div {
+  text-decoration: line-through;
+  color: var(--color-text-muted);
+}
+
 /* Tiptap editor */
 .tiptap-editor .ProseMirror {
   outline: none;