Wire witness patrol events to gt feed display

Add support for displaying gt events (from ~/gt/.events.jsonl) in the
gt feed TUI, including witness patrol activity:

- Add event symbols for patrol events (patrol_started, patrol_complete,
  polecat_checked, polecat_nudged, escalation_sent), merge events, and
  general gt events (sling, hook, handoff, mail, spawn, etc.)

- Create GtEventsSource that parses .events.jsonl format with proper
  extraction of rig/role from actor paths and human-readable message
  generation from event payloads

- Create CombinedSource that merges multiple event sources (bd activity
  and gt events) using fan-in pattern

- Update feed command to use combined source for TUI mode

- Add appropriate styling for new event types (nudges/escalations in
  red, patrol complete in green, etc.)

Example gt feed output now shows:
  09:45 ✓ witness: All polecats healthy
  09:44 ⚡ witness: nudged nux (idle 10m)
  09:40 🎯 mayor: slung gt-rbncw to furiosa

(gt-rbncw)

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

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

internal/tui/feed/view.go

@@ -249,20 +249,24 @@ func (m *Model) renderEvent(e Event) string {
 		symbolStyle = EventCreateStyle
 	case "update":
 		symbolStyle = EventUpdateStyle
-	case "complete":
+	case "complete", "patrol_complete", "merged", "done":
 		symbolStyle = EventCompleteStyle
-	case "fail":
+	case "fail", "merge_failed":
 		symbolStyle = EventFailStyle
 	case "delete":
 		symbolStyle = EventDeleteStyle
 	case "merge_started":
 		symbolStyle = EventMergeStartedStyle
-	case "merged":
-		symbolStyle = EventMergedStyle
-	case "merge_failed":
-		symbolStyle = EventMergeFailedStyle
 	case "merge_skipped":
 		symbolStyle = EventMergeSkippedStyle
+	case "patrol_started", "polecat_checked":
+		symbolStyle = EventUpdateStyle
+	case "polecat_nudged", "escalation_sent", "nudge":
+		symbolStyle = EventFailStyle // Use red/warning style for nudges and escalations
+	case "sling", "hook", "spawn", "boot":
+		symbolStyle = EventCreateStyle
+	case "handoff", "mail":
+		symbolStyle = EventUpdateStyle
 	default:
 		symbolStyle = EventUpdateStyle
 	}