Item 2 of #112548: a Desktop/dashboard build that predates server→client
requests has no response path, so every clarify/approval/sudo/secret/vault/
connection/bridge request sat for the full deadline (clarify: 300s). Only the
tour probed. Clients now advertise once per connection
(`client.capabilities {server_requests: true}`, sent by the shared TypeScript
channel on `gateway.ready`); `send()` / `send_async()` return the
error-response shape (None) at once when every WebSocket peer of the session
is a build that never advertised. Sessions with no client attached still wait
so the reconnect replay (`open_requests`) keeps working; the stdio TUI ships
with the backend and is not gated. The advertisement is dropped on disconnect.
Reviewer minors from #113227:
- tools/approval_gateway_wait.py: the verdict is the choice committed under
the approval lock while leaving the queue, so an /approve that lands after
the deadline check but before the entry is dropped is an answer, not a
timeout (the client was already acked "ok").
- tests/tui_gateway/test_protocol.py: the error-fails-fast test that only
restated pre-existing behaviour is replaced by the two capability
invariants (never advertised → fails fast; advertised → frame written,
waits, forgotten on disconnect).
- server_requests.send try/finally around event.wait already landed on main
(4371ed34a9); nothing to change.
Docs: programmatic-integration.md (advertise once per connection; method
list), tui_gateway/AGENTS.md; contracts regenerated.
f9d178f78e