Previously Phase 3 only checked the workspace-server's poll-mode short-circuit
emit shape ({"status":"queued","delivery_mode":"poll","method":"..."}); the
matching client-side classification was tested in isolation against fixture
dicts in test_a2a_response.py.
This phase closes the loop by piping the actual on-the-wire response from a
real workspace-server back through the wheel's a2a_response.parse() and
asserting it classifies as the Queued variant with the right method +
delivery_mode. A regression in EITHER the server emit shape OR the client
parser will now fail this E2E, eliminating the gap that allowed the original
"unexpected response shape" production bug to ship despite green unit tests.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>