t9 telegram: single-id allowlist delivery — notify-once via claim-send-commit, thin bot api client, lifespan-owned poller

[vlobus]

what

• delivery/telegram.py — a hand-rolled thin Bot API client (sendMessage + getUpdates) over the shared connector resilience (request_json extended with method/json_body/http_timeout), behind two Protocol halves: Messenger (what the notify job needs) and UpdateSource (what the poller reads). Telegram's HTTP-200-with-ok:false counts as failure. This supersedes the old python-telegram-bot pin (D16): two endpoints don't justify a framework that wants to own the event loop — DECISIONS entry to follow post-merge.
• delivery/formatting.py — pure formatting for HTML parse mode; every dynamic field is html-escaped at this one boundary, because the reasoning is LLM prose over untrusted headlines and must never become markup.
• delivery/poller.py — UpdatePoller long-poll loop as a lifespan-owned background task (cancellation is the stop signal, and the only thing that stops it). Default-deny allowlist: chat id and sender id must both equal the single allowlisted id, or the update is dropped in silence — strangers learn nothing. Allowlisted messages get the latest explained anomaly; the reply text arrives through an injected async callable so the poller has no DB dependency.
• ingest/jobs.py — fifth recurring job notify_anomalies (60s tick): queue = explained-but-unnotified anomalies oldest-first; once-semantics = compare-and-set on the (already-migrated) anomalies.notified_at: claim (uncommitted) → send → commit per item. A failed send rolls the claim back for the next tick; Telegram down aborts the batch as an error run. Deliberately at-least-once: a rare duplicate alert beats a silently missing one.
• store/repositories.py — explained_unnotified, latest_explained, mark_notified (the atomic claim).
• config: telegram_bot_token/base_url/chat_id/rate_per_min, required, no defaults; .env.example updated. main.py composes the client + poller; create_app gains an optional poller (PollerLike).

review fixes (subagent)

• secret redaction: httpx error text quotes the full URL — with the bot token in the path — and SourceUnavailable text is persisted to ingest_runs.detail. request_json now takes secrets=(...) and scrubs them at the wrap; applied to Telegram and the pre-existing Finnhub/Massive query-param variant of the same leak. Regression-tested.
• poller immortality: a DB blip while building a reply used to kill the background task silently and its stored exception would re-raise inside the lifespan finally, aborting the rest of teardown. The loop now absorbs any exception (backoff on failed polls, ack-and-skip on poisoned updates — never redelivered into the same crash), and shutdown suppresses a crashed task's exception.

tests

• unit: escaping (hostile <a href>/& reasoning stays literal), respx client tests (payload shape, ok:false, 5xx retry + token-redaction assertion), poller allowlist driven through run() with a scripted API (stranger silence, both-ids-must-match, crash-survival with ack).
• integration (real Postgres): the allowlisted chat receives the formatted anomaly+why exactly once across ticks, a failed send releases the claim and the next tick delivers, an unexplained anomaly is never sent.
• no test can reach api.telegram.org; no real token anywhere.
• full gate green: ruff, mypy strict, import-linter, pytest (114 passed).