Project-aware assist, link suggestions, project-scoped RAG, semantic search tool, SSE race fix

- Writing assistant: inject project notes as context (definition-tagged first), wikilink suggestions
- Link suggestions: server-side endpoint finds unlinked term occurrences, NoteEditorView sidebar panel
- Project-scoped RAG: ChatView ProjectSelector filters semantic+keyword search to selected project
- Semantic search tool: LLM search_notes upgraded to hybrid semantic (0.40 threshold) + keyword merge
- SSE race condition fix: drain remaining events after stream loop exits in chat.py and notes.py
- RAG_AUTO_SNIPPET raised 800→4000; sidebar include uses full note body; MAX_BODY_CHARS 8000→24000
- Enter-to-submit on writing assistant instruction textareas (note and task editors)
- DiffView: equal-line collapsing with 3-line context around changes

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

frontend/src/components/HistoryPanel.vue

@@ -8,6 +8,7 @@ interface NoteVersion {
   id: number;
   note_id: number;
   title: string;
+  tags: string[];
   body?: string;
   created_at: string;
 }
@@ -18,7 +19,7 @@ const props = defineProps<{
 }>();
 
 const emit = defineEmits<{
-  (e: 'restore', body: string): void;
+  (e: 'restore', body: string, tags: string[]): void;
   (e: 'close'): void;
 }>();
 
@@ -101,7 +102,7 @@ async function selectVersionItem(v: NoteVersion) {
 
 function restore() {
   if (!selectedVersion.value?.body) return;
-  emit('restore', selectedVersion.value.body);
+  emit('restore', selectedVersion.value.body, selectedVersion.value.tags ?? []);
 }
 
 onMounted(loadVersions);