search-with-proof: declarative demos, brain/executor split, kube-ax constraints

Demos are data the verifier executes (fixed build recipes, runtime+path start,
HTTP/CLI steps with captures; the canary is never referable). The agent loop with
the key never runs repository code: executor tasks without a key exchange commands
and results through presigned objects. AX capacity errors are back-pressure with at
most 2 tasks in flight; caches and builds under /workspace with a 2 GiB guard;
verifiers take one presigned archive per side. Launcher fix: private /dev in bwrap.
190 tests on the host; probe 5/5 demonstrated.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

tests/test_search_probe.py

@@ -28,7 +28,7 @@ def test_packaged_pairs_and_three_demos(tmp_path):
         assert len(demos) == 3
         assert all((s.checkout / "app.py").stat().st_size > 0 for s in sides)
         assert (sides[1].checkout / "fixed").exists()
-        assert json.loads((demos["real"] / "request.json").read_text())[0] == family
+        assert json.loads((demos["real"] / "demo.json").read_text())["steps"][0]["arguments"][0] == family
 
 
 def test_batch_workload_and_all_lanes(tmp_path, monkeypatch):