feat: Add crew session cycling fix and daemon exponential backoff (gt-ws8ol)

- Fix crew next/prev: Pass session name via key binding to avoid run-shell context issue
- Add TouchTownActivity() for town-level activity signaling
- Implement daemon exponential backoff based on activity.json:
  - 0-5 min idle → 5 min heartbeat
  - 5-15 min idle → 10 min heartbeat
  - 15-45 min idle → 30 min heartbeat
  - 45+ min idle → 60 min heartbeat (max)

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

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

internal/cmd/root.go

@@ -22,6 +22,10 @@ across distributed teams of AI agents working on shared codebases.`,
 		// Build command path: gt status, gt mail send, etc.
 		cmdPath := buildCommandPath(cmd)
 		keepalive.TouchWithArgs(cmdPath, args)
+
+		// Also signal town-level activity for daemon exponential backoff
+		// This resets the backoff when any gt command runs
+		keepalive.TouchTownActivity(cmdPath)
 	},
 }