fix: restore sidebar summary writes in writeThreadState

The PR inadvertently removed the block in writeThreadState that builds and
writes SidebarThreadSummary entries to sidebarThreadSummaryById. This meant
newly created threads and event-driven updates (message-sent, archived,
session-set, etc.) would never populate/update the sidebar summary, causing
threads to be invisible or stale in the sidebar until a separate
thread-upserted shell event arrived.

Restore the conditional write with the same equality-check optimization that
was already in place before.

Author: cursoragent

apps/web/src/store.ts

@@ -519,6 +519,8 @@ function writeThreadState(
   const nextTurnState = toThreadTurnState(nextThread);
   const previousShell = state.threadShellById[nextThread.id];
   const previousTurnState = state.threadTurnStateById[nextThread.id];
+  const previousSummary = state.sidebarThreadSummaryById[nextThread.id];
+  const nextSummary = buildSidebarThreadSummary(nextThread);
 
   let nextState = state;
 
@@ -652,6 +654,16 @@ function writeThreadState(
     };
   }
 
+  if (!sidebarThreadSummariesEqual(previousSummary, nextSummary)) {
+    nextState = {
+      ...nextState,
+      sidebarThreadSummaryById: {
+        ...nextState.sidebarThreadSummaryById,
+        [nextThread.id]: nextSummary,
+      },
+    };
+  }
+
   return nextState;
 }
 
@@ -718,7 +730,9 @@ function writeThreadShellState(
     };
   }
 
-  if (!threadSessionsEqual(state.threadSessionById[nextThread.shell.id] ?? null, nextThread.session)) {
+  if (
+    !threadSessionsEqual(state.threadSessionById[nextThread.shell.id] ?? null, nextThread.session)
+  ) {
     nextState = {
       ...nextState,
       threadSessionById: {