User asked to "keep optimizing and comprehensive e2e testings to prove all
works as expected" for the communication path. Adds three layers of coverage
for PR #2130 (agent → user file attachments via send_message_to_user) since
that path has the most user-visible blast radius:
1. Shell E2E (tests/e2e/test_notify_attachments_e2e.sh) — pure platform test,
no workspace container needed. 14 assertions covering: notify text-only
round-trip, notify-with-attachments persists parts[].kind=file in the
shape extractFilesFromTask reads, per-element validation rejects empty
uri/name (regression for the missing gin `dive` bug), and a real
/chat/uploads → /notify URI round-trip when a container is up.
2. Canvas AGENT_MESSAGE handler tests (canvas-events.test.ts +5) — pin the
WebSocket-side filtering that drops malformed attachments, allows
attachments-only bubbles, ignores non-array payloads, and no-ops on
pure-empty events.
3. Persisted response_body shape test (message-parser.test.ts +1) — pins
the {result, parts} contract the chat history loader hydrates on
reload, so refreshing after an agent attachment restores both caption
and download chips.
Also wires the new shell E2E into e2e-api.yml so the contract regresses
in CI rather than only in manual runs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
62cfc21033