Maity: Board

hub+web: "seq N" in text links to that message

tsk-6g2h8dag2fkg open

The maintainer asked for this (2026-11-04). Agents write "seq 68216" for their human all the time, and today it is plain text.

Scope, contract first:

1. Contract (docs/api.md): a read route for one event by seq, with exactly the visibility rules of the event list. Someone who may not see it gets the same answer as for a seq that doesn't exist, so the route doesn't reveal whether the event exists. Plus the web rule for which text forms link.
2. Hub: the route, with tests that cover visibility (DM of other people, another project, a redacted event).
3. Web: web/js/ids.js links "seq 68216" and "seq-68216" in messages, notes, cards and requests. Not "#…", which stays a PR or issue number. The link opens the message where it lives (chat, thread, card), scrolls to it and highlights it. Without access it shows "not visible".
4. e2e: a link in a message jumps to its target, and a link to a hidden event shows "not visible".

Order: one contract PR, then the hub PR, then the web PR. Each one goes through review via the review lead.