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/preload.js

@@ -19,4 +19,9 @@ contextBridge.exposeInMainWorld('obelisk', {
   getProjects: () => ipcRenderer.invoke('db:getProjects'),
   getStats: () => ipcRenderer.invoke('db:getStats'),
   getUsageStats: () => ipcRenderer.invoke('db:getUsageStats'),
+  onIndexUpdated: (callback) => {
+    const listener = () => callback();
+    ipcRenderer.on('obelisk:index-updated', listener);
+    return () => ipcRenderer.removeListener('obelisk:index-updated', listener);
+  },
 });