feat: Wire MQ lifecycle events to gt feed display (gt-lak31)

- Add MQ event types and logging in mrqueue/events.go
- Have refinery emit merge_started, merged, merge_failed, merge_skipped events
- Create MQEventSource to read from mq_events.jsonl
- Add MultiSource to combine events from bd activity and MQ events
- Add color coding: green for merged, red for failed
- Update feed help with MQ event symbols

Events are stored in .beads/mq_events.jsonl and displayed in the feed TUI
with appropriate symbols and colors.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/tui/feed/multi_source.go

@@ -0,0 +1,80 @@
+package feed
+
+import (
+	"sync"
+)
+
+// MultiSource combines events from multiple EventSources into a single stream.
+type MultiSource struct {
+	sources []EventSource
+	events  chan Event
+	done    chan struct{}
+	wg      sync.WaitGroup
+}
+
+// NewMultiSource creates a new multi-source that combines events from all given sources.
+func NewMultiSource(sources ...EventSource) *MultiSource {
+	m := &MultiSource{
+		sources: sources,
+		events:  make(chan Event, 100),
+		done:    make(chan struct{}),
+	}
+
+	// Start a goroutine for each source to forward events
+	for _, src := range sources {
+		if src == nil {
+			continue
+		}
+		m.wg.Add(1)
+		go m.forwardEvents(src)
+	}
+
+	// Close events channel when all sources are done
+	go func() {
+		m.wg.Wait()
+		close(m.events)
+	}()
+
+	return m
+}
+
+// forwardEvents reads from a source and forwards to the combined channel.
+func (m *MultiSource) forwardEvents(src EventSource) {
+	defer m.wg.Done()
+
+	srcEvents := src.Events()
+	for {
+		select {
+		case event, ok := <-srcEvents:
+			if !ok {
+				return
+			}
+			select {
+			case m.events <- event:
+			case <-m.done:
+				return
+			}
+		case <-m.done:
+			return
+		}
+	}
+}
+
+// Events returns the combined event channel.
+func (m *MultiSource) Events() <-chan Event {
+	return m.events
+}
+
+// Close stops all sources.
+func (m *MultiSource) Close() error {
+	close(m.done)
+	var lastErr error
+	for _, src := range m.sources {
+		if src != nil {
+			if err := src.Close(); err != nil {
+				lastErr = err
+			}
+		}
+	}
+	return lastErr
+}