fix: expose summaryStored in session status to detect silent summary loss (#1633)

Stop hook polled queueLength===0 as a proxy for summary success, but the queue
empties regardless of whether the LLM produced valid <summary> tags. Added
lastSummaryStored tracking on ActiveSession, surfaced via the /api/sessions/status
endpoint, and emit a logger.warn in the Stop hook when summaryStored===false.

Generated by Claude Code
Vibe coded by ousamabenyounes

Co-Authored-By: Claude <noreply@anthropic.com>

src/cli/handlers/summarize.ts

@@ -87,6 +87,7 @@ export const summarizeHandler: EventHandler = {
     //    This keeps the Stop hook alive (120s timeout) so the SDK agent
     //    can finish processing the summary before SessionEnd kills the session.
     const waitStart = Date.now();
+    let summaryStored: boolean | null = null;
     while ((Date.now() - waitStart) < MAX_WAIT_FOR_SUMMARY_MS) {
       await new Promise(resolve => setTimeout(resolve, POLL_INTERVAL_MS));
       try {
@@ -94,11 +95,21 @@ export const summarizeHandler: EventHandler = {
           timeoutMs: 5000
         });
         if (statusResponse.ok) {
-          const status = await statusResponse.json() as { queueLength?: number };
+          const status = await statusResponse.json() as { queueLength?: number; summaryStored?: boolean | null };
           if ((status.queueLength ?? 0) === 0) {
+            summaryStored = status.summaryStored ?? null;
             logger.info('HOOK', 'Summary processing complete', {
-              waitedMs: Date.now() - waitStart
+              waitedMs: Date.now() - waitStart,
+              summaryStored
             });
+            // Warn when the agent processed a summarize request but produced no storable summary.
+            // This is the silent-failure path described in #1633: queue empties but no summary record exists.
+            if (summaryStored === false) {
+              logger.warn('HOOK', 'Summary was not stored: LLM response likely lacked valid <summary> tags (#1633)', {
+                sessionId,
+                waitedMs: Date.now() - waitStart
+              });
+            }
             break;
           }
         }