feat(app): embed indexer in Electron with file-watching service and UI refinements

Extract schema DDL into scripts/schema.sql shared between CLI and app.
  Add an in-process chokidar-based indexer-service that watches ~/.claude/projects
  for JSONL changes, debounces, and triggers background rebuilds via a worker
  thread. Rename Usage view to Activity, flesh out MemoryDetail and SubagentDetail
  views, and refine App.vue layout/routing. The main process now starts/stops the
  indexer lifecycle and notifies renderer windows on index updates.

app/renderer/src/components/Toolbar.vue

@@ -44,8 +44,8 @@ const breadcrumbs = computed(() => {
     const m = state.memories.find(x => x.id === route.params.id);
     const filename = (m?.path || '').split('/').pop();
     crumbs.push({ label: filename, terminal: true, filename: true });
-  } else if (name === 'Usage') {
-    crumbs.push({ label: 'Usage', terminal: true });
+  } else if (name === 'Activity') {
+    crumbs.push({ label: 'Activity', terminal: true });
   }
 
   return crumbs;