fix(participation): detect deleted topics by posting into them; recreate only on thread-gone

[TOMOKI977]

Summary

This fixes a bug in hackathon-participation that the production smoke test surfaced.

The bug: a user deleted a linked topic (topic 262). /hackathon join still replied "Este hackathon ya tiene tema: …/262" with a dead link. The existence check used sendChatAction, and Telegram accepts that call even for a deleted thread, so it could never detect the deletion.

The fix: the bot now checks an existing linked topic by doing the real action, which is posting the analysis into it (post + re-pin via postAnalysisAndLinkTopic).

• Post succeeds: the topic is live. The bot replies "Este hackathon ya tiene tema: ", and the analysis is re-posted and pinned there.
• Post fails with thread-gone: this is a 400 whose description matches message thread not found / TOPIC_ID_INVALID / TOPIC_DELETED. The topic is deleted, so the existing path runs: claim, create, link, post/pin, confirm.
• Any other failure (a closed topic, 403/no rights, another 4xx, 5xx, 429, or something unexpected) is logged as topic-check-failed. The bot replies with the link and does not recreate, so a live topic is never duplicated.

Changes

• src/adapters/telegram/send-failure.ts: new classifyPublishFailure, which emits thread-gone only for a 400 with a thread-gone description. A 403 with the same wording stays rejected. classifyTelegramFailure is unchanged, so the alert sender behaves as before.
• src/adapters/telegram/chat-publisher.ts: only post() uses the new classifier. pin, unpin and clearButtons are unchanged.
• src/domain/errors.ts: adds PublishFailureClass = AlertSendFailureClass | "thread-gone".
• src/domain/usecases/participate-in-hackathon.ts: only thread-gone recreates.
• src/domain/usecases/run-hackathon-job.ts: thread-gone is handled like rejected (no retry).
• ForumTopicManager.probe is removed from the port, the adapter, the fakes and the tests.
• Docs: proposal.md, design.md and the spec now describe the post-based check and its residual risk. If Telegram's deleted-thread wording differs, the topic is not recreated, which is the safe side, and the smoke test confirms the wording.

Review

• A first review found a CRITICAL issue: any 4xx was being treated as "deleted", so a closed topic or a 403 could create a duplicate. I corrected it, and a fresh review over all 16 changed paths approved the change.
• One deferred warning remains: the thread-gone line in run-hackathon-job.ts has no test.

Tests

• Strict TDD.
• The full suite passes (1027 tests) and the typecheck is clean.

🤖 Generated with Claude Code