fix(memory-core): prevent dreaming-narrative session leaks (GitHub #66358)

Root cause: `runDreamingSweepPhases` passed `params.nowMs` through to each
phase without normalizing it first. Each phase recomputed `Date.now()` at
call time, producing a slightly different timestamp than the session key
used by `generateAndAppendDreamNarrative`. The resulting session key
mismatch meant the `deleteSession` call cleaned up a different (or
non-existent) key than the one that was created.

Fix:
- Normalize `nowMs` once at the top of `runDreamingSweepPhases` and
  pass the consistent value to all phases.
- Add a defensive `deleteSession` call in `runDreamingSweepPhases` for
  each phase after `runLightDreaming`/`runRemDreaming` completes. This
  acts as a safety net even if the narrative function's primary cleanup
  is skipped.
- Guard the `finally` block in `generateAndAppendDreamNarrative` with
  `if (params.subagent)` to prevent TypeError if the subagent runtime
  becomes unavailable mid-flight.

This fixes the observed session list pollution where
`dreaming-narrative-*-<timestamp>` entries accumulated indefinitely.

extensions/memory-core/src/dreaming-narrative.ts

@@ -911,7 +911,7 @@ export async function generateAndAppendDreamNarrative(params: {
       `memory-core: narrative generation failed for ${params.data.phase} phase: ${formatErrorMessage(err)}`,
     );
   } finally {
-    if (runId && waitStatus === "timeout") {
+    if (params.subagent && runId && waitStatus === "timeout") {
       try {
         const settle = await params.subagent.waitForRun({
           runId,
@@ -929,12 +929,15 @@ export async function generateAndAppendDreamNarrative(params: {
       }
     }
 
-    try {
-      await params.subagent.deleteSession({ sessionKey });
-    } catch (cleanupErr) {
-      params.logger.warn(
-        `memory-core: narrative session cleanup failed for ${params.data.phase} phase: ${formatErrorMessage(cleanupErr)}`,
-      );
+    // Guard against subagent becoming unavailable mid-flight (throws TypeError without this).
+    if (params.subagent) {
+      try {
+        await params.subagent.deleteSession({ sessionKey });
+      } catch (cleanupErr) {
+        params.logger.warn(
+          `memory-core: narrative session cleanup failed for ${params.data.phase} phase: ${formatErrorMessage(cleanupErr)}`,
+        );
+      }
     }
 
     await scrubDreamingNarrativeArtifacts(params.logger).catch((scrubErr: unknown) => {

extensions/memory-core/src/dreaming-phases.ts

@@ -1641,6 +1641,9 @@ export async function runDreamingSweepPhases(params: {
   subagent?: Parameters<typeof generateAndAppendDreamNarrative>[0]["subagent"];
   nowMs?: number;
 }): Promise<void> {
+  // Normalize nowMs once so all phase timestamps and narrative session keys are consistent.
+  const sweepNowMs = Number.isFinite(params.nowMs) ? params.nowMs : Date.now();
+
   const light = resolveMemoryLightDreamingConfig({
     pluginConfig: params.pluginConfig,
     cfg: params.cfg,
@@ -1652,8 +1655,18 @@ export async function runDreamingSweepPhases(params: {
       config: light,
       logger: params.logger,
       subagent: params.subagent,
-      nowMs: params.nowMs,
+      nowMs: sweepNowMs,
     });
+    // Defensive cleanup: ensure the light-phase narrative session is deleted even if
+    // generateAndAppendDreamNarrative's primary cleanup was skipped due to an error.
+    if (params.subagent) {
+      const lightSessionKey = `dreaming-narrative-light-${sweepNowMs}`;
+      await params.subagent
+        .deleteSession({ sessionKey: lightSessionKey })
+        .catch(() => {
+          // Swallow errors — this is best-effort cleanup.
+        });
+    }
   }
 
   const rem = resolveMemoryRemDreamingConfig({
@@ -1667,8 +1680,17 @@ export async function runDreamingSweepPhases(params: {
       config: rem,
       logger: params.logger,
       subagent: params.subagent,
-      nowMs: params.nowMs,
+      nowMs: sweepNowMs,
     });
+    // Defensive cleanup: ensure the REM-phase narrative session is deleted.
+    if (params.subagent) {
+      const remSessionKey = `dreaming-narrative-rem-${sweepNowMs}`;
+      await params.subagent
+        .deleteSession({ sessionKey: remSessionKey })
+        .catch(() => {
+          // Swallow errors — this is best-effort cleanup.
+        });
+    }
   }
 }