A deployment registered while a module- or class-scoped fixture is being set up
was bound to whichever test asked for the fixture first, so every later test in
the module shared that partition. A session-scoped fixture is set up by every
xdist worker, so its deployment could never have one owner at all.
The e2e conftest now wraps pytest_fixture_setup and records the node the fixture
is scoped to: registrations made during a module or class fixture's setup carry
that node's slug, and a session- or package-scoped one has no owner and stays
live. The registration seam test moves from tests/e2e to the cache harness tests
beside the rest of the attribution coverage.
Replaces the test-side fixture transport with an in-process provider-edge
HTTP server the proxy's deployments point their api_base at. Record forwards
provider calls verbatim and writes them to the bundle; replay answers them
from the bundle with zero provider calls while key auth, routing, cost
calculation, and spend-log writes still execute against the live proxy and
database. Drift comes back as HTTP 599 naming the computed and closest
recorded keys. Request headers are never stored and responses are kept
byte-identical between modes from the proxy's side of the socket.
