feat(participation): topic creation infrastructure, claim and migration 0004 (hackathon-participation 1a/3)

[TOMOKI977]

Summary

PR 1a of 3 for change 4, hackathon-participation. When an admin confirms, the bot creates a 🏆 <name> forum topic, then posts and pins the analysis there.

This PR adds only the infrastructure, with tests. Nothing uses it yet, so bot behavior is unchanged.

• Planning docs: the exploration, proposal, specs, design and tasks for the change, under openspec/changes/hackathon-participation/.
• migrations/0004_hackathon_participation.sql: adds two columns and nothing else. topic_claim_until holds the anti-duplicate claim and general_message_id holds the General analysis message id.
• src/adapters/d1/hackathon-analysis-repo.ts:
  • The claim is a single conditional UPDATE: a compare-and-set with a 60 s TTL.
  • The claim can be released, and the general message id can be read and written.
  • Everything is scoped by team_id with bound parameters.
  • The existing upserts never write the new columns.
• ForumTopicManager port and src/adapters/telegram/forum-topic-manager.ts:
  • create classifies the outcome as missing rights, not a forum, rejected, or uncertain.
  • probe uses sendChatAction with the thread id. It reports deleted only for a known thread-gone error; anything ambiguous counts as live, so a duplicate topic is never created.
  • Every call has a 10 s timeout.
• ChatPublisher:
  • post takes an optional { participateSlug }, which adds the "✅ Participamos" button (hp:<slug>, at most 64 bytes).
  • New clearButtons.
  • The button label comes from the Spanish copy catalog.
• Fakes for the new ports.

Review

A bounded review ran at high risk with all 4 lenses. There are no severe findings. Risk and resilience found nothing. Four advisory warnings will be fixed first thing in PR 1b:

ID	Issue
R2-001	A ports.ts comment ended up detached from ChatPublisher.post
R2-002	design.md and a comment say the claim expires at < now, but the code uses <= now
R3-001	No test preserves a non-null generalMessageId across a refresh
R3-002	The fake repo's save replaces the whole row, unlike the D1 upserts

Tests

• Strict TDD.
• The full suite passes (916 tests) and typecheck is clean.
• The remote D1 migration runs through the CI deploy, as in earlier changes.

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