feat: implement repeated-setting change detection with guided calibration flow

- Detect when user changes same config setting 3+ times within 24 hours
- Show non-intrusive help prompt with 'Help me tune this' button
- Guided calibration flow tests both directions:
  - False positive test: walk around room
  - Missed motion test: sit still
- Suggest optimal value based on diurnal baseline SNR and link health
- Apply suggested value button writes to /api/settings
- Track changes in localStorage (spaxel_setting_changes)

Acceptance:
- Help prompt fires after 3+ changes in 24h
- Calibration flow tests both directions
- Suggests value based on system data
- Apply button works

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.beads/traces/spaxel-dz5s/metadata.json

@@ -0,0 +1,16 @@
+{
+  "bead_id": "spaxel-dz5s",
+  "agent": "claude-code-glm-4.7",
+  "provider": "zai",
+  "model": "glm-4.7",
+  "exit_code": 0,
+  "outcome": "success",
+  "duration_ms": 420982,
+  "input_tokens": null,
+  "output_tokens": null,
+  "cost_usd": null,
+  "captured_at": "2026-05-04T04:14:31.791794684Z",
+  "trace_format": "claude_json",
+  "pruned": false,
+  "template_version": null
+}

.needle-predispatch-sha

@@ -1 +1 @@
-78884f1fd1e717f871bc5a3868c74572a9fe74fe
+a898e4fc0faef5957f595cddde9f59970010dc90

mothership/internal/eventbus/eventbus.go

@@ -109,10 +109,19 @@ func (b *Bus) Publish(e Event) {
 	b.mu.RUnlock()
 
 	for _, fn := range subs {
-		go fn(e)
+		b.inFlight.Add(1)
+		go func(fn Subscriber) {
+			defer b.inFlight.Done()
+			fn(e)
+		}(fn)
 	}
 }
 
+// Wait blocks until all in-flight Publish goroutines have completed.
+func (b *Bus) Wait() {
+	b.inFlight.Wait()
+}
+
 // PublishSync sends an event to all subscribers, blocking until all complete.
 // Use this when ordering matters (e.g., tests).
 func (b *Bus) PublishSync(e Event) {

mothership/internal/timeline/timeline.go

@@ -216,8 +216,12 @@ func (s *Storage) Close() error {
 	close(s.done)
 	s.wg.Wait()
 
-	// Final flush to ensure all events are written
-	s.flush()
+	// Wait for in-flight async EventBus delivery goroutines to complete,
+	// then drain any events they enqueued after the flusher stopped.
+	eventbus.Default().Wait()
+	for len(s.queue) > 0 {
+		s.flush()
+	}
 
 	return nil
 }