feat(plane): per-task egress policy; receiver by name through the gateway

Agent Substrate's egress gateway denies an actor without an EgressPolicy, so
no task could deliver its artifacts or reach a model. egress.py grants each
task exactly: http/80 to ousast-receiver.ax-system.svc.cluster.local, and
TLS passthrough/443 to the bound Workspaces' https Git hosts and the bound
Model's openultrasast.io/egress-hosts (api.deepseek.com for deepseek-flash).
No IPs, no wildcards, no https (MITM) rules.

The reconciler writes the policy with kubectl-ate between ax apply and
resume, reads it back, waits OUSAST_EGRESS_SETTLE (11 s, the gateway's
cached deny), and after ax delete task confirms the policy went with its
actor (kubectl-ate has no delete verb; the store cascades).

The receiver is a selector-less Service (ops/ax/receiver-service.yaml.tmpl,
applied by up.sh together with the no-build agentgateway egress gateway)
on port 18090 of the host. Measured live: the gateway checks the policy on
Host but connects to the address the actor dialled, so the runner dials the
Service's ClusterIP (OUSAST_ARTIFACT_DIAL) with the receiver's name as Host.
The runner now labels its delivery with the Run's task name (OUSAST_TASK),
which is what the receiver accepts; the ax Task name was refused with 403.
The Receiver moved to egress.py to keep reconciler.py at 460 lines.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

tests/test_plane_runner.py

@@ -244,6 +244,10 @@ def test_output_dir_is_delivered_as_a_tar_with_the_headers(
     assert headers["Content-Type"] == "application/x-tar"
     assert headers["X-Ousast-Task"] == "stub"
     assert headers["X-Ousast-Run"] == "validation-46"
+    receiver.posts.clear()
+    again = {"OUSAST_ARTIFACT_URL": receiver.url, "OUSAST_TASK": "facts", "OUSAST_STATE_DIR": str(tmp_path / "again-state")}
+    code, _ = run_main(monkeypatch, tmp_path / "again", files_workspace_yaml(), **again)
+    assert code == 0 and receiver.posts[0][0]["X-Ousast-Task"] == "facts", "the Run's task name, not the ax Task's"
     with tarfile.open(fileobj=io.BytesIO(body), mode="r:") as archive:
         names = sorted(archive.getnames())
         summary = archive.extractfile("summary.json")