fix: prevent SHIPPABLE stories and wrong READY state on failed tasks

Three related bugs fixed:

1. maybeUnblockParent: guard against promoting QUEUED leaf tasks (no
   subtasks) to READY. The vacuously-true 'all subtasks done' check was
   advancing tasks that stalled in QUEUED (due to a prior SQLite lock
   error) to READY on server restart via RecoverStaleBlocked, despite
   having only failed executions and no commits.

2. checkStoryCompletion: require COMPLETED (not just READY) for all
   top-level tasks before advancing a story to SHIPPABLE. READY means
   the checker agent is still pending or the task awaits human review;
   a story with READY tasks is not ready to ship.

3. handleAcceptTask: call CheckStoryCompletion after a task is accepted
   so stories with parent tasks (whose subtasks are all done and then
   the parent is manually accepted) can auto-advance to SHIPPABLE.

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

1 files changed, 13 insertions, 2 deletions

diff --git a/internal/executor/executor.go b/internal/executor/executor.go
index 8257f31..384a323 100644
--- a/internal/executor/executor.go
+++ b/internal/executor/executor.go
@@ -543,6 +543,12 @@ func (p *Pool) handleRunResult(ctx context.Context, t *task.Task, exec *storage.
 // a terminal success state and transitions the story to SHIPPABLE if so.
 // Subtasks are intentionally excluded — a parent task reaching READY/COMPLETED
 // already accounts for its subtasks.
+// CheckStoryCompletion is the exported entry point for story completion checks
+// called from outside the package (e.g. the API accept handler).
+func (p *Pool) CheckStoryCompletion(ctx context.Context, storyID string) {
+	p.checkStoryCompletion(ctx, storyID)
+}
+
 func (p *Pool) checkStoryCompletion(ctx context.Context, storyID string) {
 	story, err := p.store.GetStory(storyID)
 	if err != nil {
@@ -566,8 +572,8 @@ func (p *Pool) checkStoryCompletion(ctx context.Context, storyID string) {
 			continue // subtasks are covered by their parent
 		}
 		topLevelCount++
-		if t.State != task.StateCompleted && t.State != task.StateReady {
-			return // not all top-level tasks done
+		if t.State != task.StateCompleted {
+			return // not all top-level tasks done; READY alone is not sufficient (checker may be pending)
 		}
 	}
 	if topLevelCount == 0 {
@@ -1251,6 +1257,11 @@ func (p *Pool) maybeUnblockParent(parentID string) {
 		p.logger.Error("maybeUnblockParent: list subtasks", "parentID", parentID, "error", err)
 		return
 	}
+	// A task with no subtasks was never blocked by subtask delegation — don't promote it.
+	// This prevents incorrectly promoting leaf tasks that are stuck in QUEUED to READY.
+	if len(subtasks) == 0 {
+		return
+	}
 	for _, sub := range subtasks {
 		if sub.State != task.StateCompleted {
 			return