perf(web): add dashboard hydration observability

apps/web/src/App.tsx

@@ -10,6 +10,7 @@ import type { DashboardRuntimeState } from "$lib/server/dashboard";
 import {
   attachDashboardRefreshLifecycle,
   collectVisibleDashboardModelIds,
+  createDashboardPerformanceMarks,
   createDashboardRefreshDelay,
   createDashboardTileSnapshotStore,
   createDashboardTileBackoff,
@@ -174,6 +175,7 @@ export default function App() {
     let lastRefreshIntervalMs = dashboardFallbackRefreshIntervalMs;
     let hydrationRun = 0;
     const requestAborter = createDashboardRequestAborter();
+    const performanceMarks = createDashboardPerformanceMarks();
     const refreshDelay = createDashboardRefreshDelay();
     const tileBackoff = createDashboardTileBackoff();
     const tileSnapshotStore = createDashboardTileSnapshotStore(
@@ -222,6 +224,7 @@ export default function App() {
 
         if (cancelled || shellSignal.aborted || refreshPaused()) return;
         refreshDelay.recordSuccess();
+        performanceMarks.markShellLoad();
         const restored = restoreDashboardTileSnapshots(
           nextDashboard,
           nextDashboard.state === "ready"
@@ -319,6 +322,8 @@ export default function App() {
           }
         },
         items: tiles,
+        onAllItemsSettled: () => performanceMarks.markAllTilesSettled(),
+        onVisibleItemsSettled: () => performanceMarks.markVisibleTilesReady(),
         signal,
         waitForIdle: () =>
           waitForDashboardHydrationIdle({
@@ -367,6 +372,7 @@ export default function App() {
           ...snapshotContext,
           response: readyTileResponse,
         });
+        performanceMarks.markFirstTileReady();
         return "ready";
       } catch (error) {
         if (!isAbortError(error) && !cancelled) {