jerry/buzz

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Bradley Axen 6c388bde62 feat(relay): accept typing indicators over HTTP POST /events (#8207 )

## Summary

Agents hosted inside the Buzz app sign their own events but don't hold a
WebSocket, so they couldn't show "typing…" in a channel. `POST /events`
rejected kind 20002 (typing indicator) with `restricted: unknown event
kind`.

Now, when `POST /events` receives a kind 20002 event, the bridge passes
it to the same channel broadcast the WebSocket path uses. Live
subscribers in the channel get the pulse. Nothing is written to
Postgres.

Before broadcasting, the relay checks, in order:
- the event has an `h` tag naming the channel
- the serialized event is at most 2 KiB (real typing events are ~600
bytes). Measuring the whole JSON, not just content and tag values, means
piling on empty tags can't get around the cap
- the signature and id are valid
- bans and timeouts
- the community write fence (over HTTP, a quiescing community's host
already fails to bind with a 404, so this catches quiescing that starts
after the tenant is bound)
- the sender is a channel member, or the channel is open (same rule as
WebSocket)
- the signer is the pubkey that authenticated the request (checked
first; a mismatch returns 403)

The existing HTTP admission rate limit and relay-membership gate still
run before any of this. Other ephemeral kinds are still rejected over
HTTP. `publish_channel_ephemeral` is the old WebSocket channel-broadcast
code moved into a shared helper, so both paths use the same membership
check and fan-out.

Unlike the WebSocket path, HTTP requires the `h` tag. Over WebSocket, a
20002 with no channel goes to every subscriber.

Points left for review:
- HTTP typing pulses count against the same per-pubkey HTTP quota as
message posts (default 300/min). One pulse every 3 s is 20/min per
active channel.
- A failed Redis publish is logged and the POST still returns `accepted:
true`, same as the WebSocket path. A pulse is resent every 3 s and
expires after 8 s, so a retry would only resend a stale pulse.

The `sadscan:disable` comment on an existing test URL in `ingest.rs` is
there because the secret scanner reads every file a commit touches. It
uses the same form as the other local test fixtures in the repo.

### Related issue

Needed for Agents2 typing indicators in buzz-app. The client PR depends
on this one and will follow as a draft.

### Testing

- 9 new Postgres-backed tests in `api/typing_postgres_tests.rs` cover
these cases: a member's pulse is published and not stored; a non-member
gets a 400; a timed-out member gets a 403; a signer mismatch gets a 403;
a missing `h` tag gets a 400; a tampered event gets a 400; kind 20001 is
still rejected; oversized events get a 400 (2 KiB of content, one 2 KiB
tag value, or `h` + 10k empty tags); a community that starts quiescing
after the tenant is bound gets a 400 `community writes are fenced`, and
nothing is published. Two mutation checks: with the fence removed, the
fence test fails; with the old content-plus-tag-values cap, the
empty-tags case is accepted and the test fails.
- The full buzz-relay Postgres lane on 27b5a294: 386/387 pass. The one
failure is
`boot_lifecycle::hanging_redis_peer_times_out_before_the_health_listener_binds`:
it went over its timing slack under full-suite load (8.03 s) and passed
when rerun alone.
- buzz-relay unit tests pass (1476). One mesh demo test timed out once
under load and passed when rerun alone.
- `cargo clippy -p buzz-relay -p buzz-cli -p buzz-acp --all-targets -D
warnings` is clean.
- Live test against a local relay built from this branch (27b5a294), run
by ART at baxen's request as the sign-off test. alice subscribed over
WebSocket to kind 20002 in a private channel; bob (a bot member with no
WebSocket) and carol (outsider) used `POST /events` with NIP-98. 16/16
checks passed:
- bob's top-level pulse → 200 `accepted: true`, and alice received it
live
- bob's thread pulse (`h` + root `e` + reply `e`, the buzz-acp shape) →
delivered with tags intact
- 2 KiB content, a 2 KiB tag value, or `h` + 10k empty tags → 400
`typing indicator too large`; alice received nothing
- carol → 400 `restricted: not a channel member`; alice received nothing
  - carol posting an event signed by bob → 403
  - no `h` tag → 400; kind 20001 → 400 `only accepted via WebSocket`
  - 0 kind-20002 rows in Postgres afterwards

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Signed-off-by: Bradley Axen <baxen@squareup.com>
Signed-off-by: ART <ea39c1c8acf57180161ef4ba4ed68abf8589f5291956b909a5aa991fc66664ca@buzz.block.builderlab.xyz>
Signed-off-by: Honey <8e307ae0076a4dab6b94b036ea3edc7e08f823a625269c1e6919e881a048b4d2@buzz.block.builderlab.xyz>
Co-authored-by: Honey <8e307ae0076a4dab6b94b036ea3edc7e08f823a625269c1e6919e881a048b4d2@buzz.block.builderlab.xyz>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: ART <ea39c1c8acf57180161ef4ba4ed68abf8589f5291956b909a5aa991fc66664ca@buzz.block.builderlab.xyz>