Fix Codex review issues: phase-timeout mutation race and missing backfill

P1 (phase-timeout mutation race): withPhaseTimeout now stores the still-running
phase promise in _danglingPhasePromise when a timeout fires. Each loop iteration
drains that promise (with try/catch) before starting new work, preventing the
timed-out phase from mutating state concurrently with the next iteration.

P2 (verification_status backfill): Schema migration v17 now runs a backfill UPDATE
after adding the new column, deriving verification_status from existing
verification_evidence rows. Projects upgraded mid-slice will have correct
all_pass/partial/all_fail values immediately rather than empty strings that
bypass the prior-task guard.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/resources/extensions/sf/auto/loop.ts

@@ -95,9 +95,19 @@ function checkMemoryPressure(): { pressured: boolean; heapMB: number; limitMB: n
   return { pressured: pct > MEMORY_PRESSURE_THRESHOLD, heapMB, limitMB, pct };
 }
 
+/**
+ * Tracks the dangling phase promise from the most recent timeout so the next
+ * iteration can drain it before proceeding. Promise.race() rejects on timeout
+ * but does not cancel the underlying async work; draining here prevents the
+ * timed-out phase from mutating state concurrently with the next iteration.
+ */
+let _danglingPhasePromise: Promise<unknown> | null = null;
+
 /**
  * Wrap a phase function with a timeout. Rejects with an Error whose message
  * starts with "phase-timeout:" so the blanket catch can handle it specially.
+ * Stores the still-running phase promise in _danglingPhasePromise so the caller
+ * can drain it before starting a new iteration.
  */
 async function withPhaseTimeout<T>(
   name: string,
@@ -105,6 +115,7 @@ async function withPhaseTimeout<T>(
   timeoutMs: number,
 ): Promise<T> {
   let timer: ReturnType<typeof setTimeout> | undefined;
+  const phasePromise = fn();
   const timeout = new Promise<never>((_, reject) => {
     timer = setTimeout(
       () => reject(new Error(`phase-timeout:${name}`)),
@@ -112,8 +123,12 @@ async function withPhaseTimeout<T>(
     );
   });
   try {
-    const result = await Promise.race([fn(), timeout]);
-    return result;
+    return await Promise.race([phasePromise, timeout]);
+  } catch (err) {
+    if (err instanceof Error && err.message.startsWith("phase-timeout:")) {
+      _danglingPhasePromise = phasePromise;
+    }
+    throw err;
   } finally {
     if (timer !== undefined) clearTimeout(timer);
   }
@@ -232,6 +247,16 @@ export async function autoLoop(
       break;
     }
 
+    // ── Drain any dangling phase promise before starting new work ──
+    // Promise.race() on timeout does not cancel the underlying async fn; that
+    // fn keeps running and may mutate state after the loop has advanced.
+    // Awaiting its completion here ensures no concurrent state writes.
+    if (_danglingPhasePromise !== null) {
+      const dangling = _danglingPhasePromise;
+      _danglingPhasePromise = null;
+      try { await dangling; } catch { /* ignore — result is irrelevant */ }
+    }
+
     try {
       // ── Blanket try/catch: one bad iteration must not kill the session
       const prefs = deps.loadEffectiveSFPreferences()?.preferences;

src/resources/extensions/sf/sf-db.ts

@@ -1003,6 +1003,32 @@ function migrateSchema(db: DbAdapter): void {
 
     if (currentVersion < 17) {
       ensureColumn(db, "tasks", "verification_status", `ALTER TABLE tasks ADD COLUMN verification_status TEXT NOT NULL DEFAULT ''`);
+      // Backfill verification_status from existing verification_evidence rows so the
+      // prior-task guard works on databases upgraded mid-project (not just new ones).
+      db.exec(`
+        UPDATE tasks
+        SET verification_status = CASE
+          WHEN (SELECT COUNT(*) FROM verification_evidence ve
+                WHERE ve.milestone_id = tasks.milestone_id
+                  AND ve.slice_id    = tasks.slice_id
+                  AND ve.task_id     = tasks.id) = 0
+            THEN ''
+          WHEN (SELECT COUNT(*) FROM verification_evidence ve
+                WHERE ve.milestone_id = tasks.milestone_id
+                  AND ve.slice_id    = tasks.slice_id
+                  AND ve.task_id     = tasks.id
+                  AND ve.exit_code  != 0) = 0
+            THEN 'all_pass'
+          WHEN (SELECT COUNT(*) FROM verification_evidence ve
+                WHERE ve.milestone_id = tasks.milestone_id
+                  AND ve.slice_id    = tasks.slice_id
+                  AND ve.task_id     = tasks.id
+                  AND ve.exit_code   = 0) > 0
+            THEN 'partial'
+          ELSE 'all_fail'
+        END
+        WHERE tasks.status IN ('complete', 'done')
+      `);
       db.prepare("INSERT INTO schema_version (version, applied_at) VALUES (:version, :applied_at)").run({
         ":version": 17,
         ":applied_at": new Date().toISOString(),