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.

scripts/indexer.mjs

@@ -246,12 +246,29 @@ function indexHistory(db) {
 }
 
 const BUILD_DEBOUNCE_MS = 30000;
+const APP_HEARTBEAT_FRESH_MS = 60000;
+
+function shouldSkipBuild(db, { now = Date.now() } = {}) {
+  const appHeartbeat = db.prepare("SELECT mtime FROM index_state WHERE jsonl_path='__app_heartbeat__'").get();
+  const appSuccessfulBuild = db.prepare("SELECT mtime FROM index_state WHERE jsonl_path='__app_last_successful_build__'").get();
+  if (
+    appHeartbeat && now - appHeartbeat.mtime < APP_HEARTBEAT_FRESH_MS &&
+    appSuccessfulBuild && now - appSuccessfulBuild.mtime < APP_HEARTBEAT_FRESH_MS
+  ) {
+    return { skip: true, reason: 'app_successful_build' };
+  }
+  const last = db.prepare("SELECT mtime FROM index_state WHERE jsonl_path='__last_build__'").get();
+  if (last && now - last.mtime < BUILD_DEBOUNCE_MS) {
+    return { skip: true, reason: 'recent_build' };
+  }
+  return { skip: false };
+}
 
 function buildIndex({ force = false } = {}) {
   const db = openDb();
   if (!force) {
-    const last = db.prepare("SELECT mtime FROM index_state WHERE jsonl_path='__last_build__'").get();
-    if (last && Date.now() - last.mtime < BUILD_DEBOUNCE_MS) { db.close(); return; }
+    const skip = shouldSkipBuild(db);
+    if (skip.skip) { db.close(); return; }
   }
 
   if (force) {
@@ -286,4 +303,4 @@ function buildIndex({ force = false } = {}) {
   db.close();
 }
 
-export { buildIndex, inferProjectPath, refreshSessionProjectPaths };
+export { buildIndex, inferProjectPath, refreshSessionProjectPaths, shouldSkipBuild };