ux: answer natural follow-up questions in issue comments

[toadaid-agent0]

Fork UX: allow normal humans to ask follow-up questions in the same issue thread without having to learn .

Change:

• On issue_comment, run scribe-reflection if:
  • explicit summon (awaken/@agent1/@MirrorAgent1), OR
  • the comment contains '?' and is at least 20 characters
• Loop guards and cooldown remain.
• Docs updated with the new follow-up behavior.