fix(vault): suppress stale error toast on stop + count unenriched docs in scan

- AddError() now skips broadcast after Finish() to prevent cancelled
  goroutines from emitting error events to UI after user stops enrichment
- batchSummarize skips AddError when context is cancelled (expected on stop)
- Rescan always re-enqueues unenriched docs alongside new/updated files,
  worker-level dedup prevents double-processing

internal/http/vault_handlers.go

@@ -204,14 +204,15 @@ func (h *VaultHandler) handleRescan(w http.ResponseWriter, r *http.Request) {
 	// and AddDone calls are not dropped by the !running guard.
 	total := result.New + result.Updated
 
-	// If no new/updated files, check for unenriched docs and re-enqueue them.
-	// This handles the case where previous enrichment failed (e.g. provider timeout).
-	if total == 0 && h.enrichWorker != nil {
+	// Always re-enqueue docs that lack summaries (failed previous enrichment).
+	// Worker-level dedup (DocID+ContentHash) prevents double-processing docs
+	// that are also in PendingEvents from the current scan.
+	if h.enrichWorker != nil {
 		enqueued, err := h.enrichWorker.EnqueueUnenriched(ctx, tenantID, wsPath, h.eventBus, 0)
 		if err != nil {
 			slog.Warn("vault.rescan: enqueue_unenriched failed", "tenant", tenantID, "error", err)
 		} else if enqueued > 0 {
-			total = enqueued
+			total += enqueued
 			result.Reenqueued = enqueued
 			slog.Info("vault.rescan: re-enqueued unenriched docs", "tenant", tenantID, "count", enqueued)
 		}

internal/vault/enrich_progress.go

@@ -78,9 +78,13 @@ func (p *EnrichProgress) Start(total int, tenantID uuid.UUID) {
 
 // AddError increments error count and broadcasts an error event.
 // Used when enrichment fails for a document (e.g., LLM retries exhausted).
+// Suppressed after Finish() to prevent stale errors from cancelled goroutines.
 func (p *EnrichProgress) AddError(errMsg string) {
 	p.mu.Lock()
 	defer p.mu.Unlock()
+	if !p.running {
+		return
+	}
 	p.errorCount++
 	p.lastError = errMsg
 	p.broadcast(EnrichEvent{

internal/vault/enrich_worker.go

@@ -460,7 +460,8 @@ func (w *EnrichWorker) batchSummarize(ctx context.Context, provider providers.Pr
 	})
 	if err != nil {
 		slog.Warn("vault.enrich: batch_summarize", "count", len(paths), "err", err)
-		if w.progress != nil {
+		// Don't report context cancellation as enrichment error — expected during stop.
+		if w.progress != nil && ctx.Err() == nil {
 			w.progress.AddError(fmt.Sprintf("batch summarize failed: %v", err))
 		}
 		return nil