The relay outbound surface had send/edit/typing but no way to act on a
SHARED-identity capability (e.g. a Discord interaction follow-up token,
~15min) that the connector captured + stripped at the edge. Under A2 that
credential never reaches the gateway, so the gateway can't just 'send with
the token' — it needs a semantic op naming the session it's already in.
Adds the follow_up op end to end on the gateway side:
- RelayTransport.send_follow_up(action): protocol method. Action carries
op='follow_up' + session_key + kind + content (+ metadata) and NO token.
- RelayAdapter.send_follow_up(session_key, kind, content, metadata): builds
that action and returns a SendResult. The connector resolves the real
capability (its resolveOutboundCapability), enforces the tenant match so
tenant B can't wield tenant A's capability, and egresses; success=False
when the capability is absent/expired/mismatched (nothing to retry — a
leaked gateway holds zero capability material).
- StubConnector records follow_ups + a canned next_follow_up_result.
Tests: round-trips without a token; the wire action carries only session
refs (no credential value field — the 'kind' string is a type ref, not the
secret); failure surfaces when the connector can't resolve; no-transport
fails cleanly. 55 passed. §4 doc entry follows in the contract-rewrite commit.
3db9b3e616