test: gate V1 side files and V3 legacy receipts; early output rejection

- analyze_jet_cv_continuation: samples are analyzed only if the sibling
  re*_s*.json receipt is the same case with run_status COMPLETE and
  source_recheck UNCHANGED; receipts without run_status (pre-recheck
  runners) are refused unless --legacy-receipts, and labelled
  LEGACY_NO_FINAL_SOURCE_RECHECK. Results carry receipt_gate.
- V3: receipts are schema 2 and need source_recheck UNCHANGED; a missing
  recheck is accepted only for frozen-mode schema 1 receipts whose
  run_case.py hash is one of the pre-recheck runners (9805383, 2cf9853,
  db3d098; hashes checked against git history in a test).
- V1/V3 refuse --output inside the checkout before source checks or CUDA
  (shared source_provenance.reject_output_inside).
- A failing recheck is recorded as RECHECK_FAILED (still invalid); the
  in-run V1 receipt write is tmp+replace.
Negative host tests for each gate. No threshold, solver or evidence edits.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/test_jet_cv_measurements.py

@@ -151,6 +151,8 @@ class Measurements(unittest.TestCase):
             (path / "samples_s2.json").write_text(
                 json.dumps(dict(case=c, sample_file="samples_s2.npz"))
             )
+            (path / f"re{c['re_d']}_s2.json").write_text(json.dumps(
+                dict(case=c, run_status="COMPLETE", source_recheck="UNCHANGED")))
             np.savez(
                 path / "samples_s2.npz",
                 t_reference=t,
@@ -163,6 +165,7 @@ class Measurements(unittest.TestCase):
                 velocity_error=np.zeros(n),
             )
             result = analyze(path)
+            self.assertEqual(result["receipt_gate"], "COMPLETE_SOURCE_UNCHANGED")
             self.assertEqual(len(result["windows"]), 32)
             np.testing.assert_allclose(
                 result["windows"][0]["normalized_cv_residual"], 0, atol=1e-14
@@ -178,5 +181,36 @@ class Measurements(unittest.TestCase):
         np.testing.assert_allclose(integrate(t, y), [112, 8], atol=1e-15)
 
 
+    def test_receipt_gate_refuses_incomplete_invalid_and_unmarked_legacy(self):
+        import json
+        from analyze_jet_cv_continuation import receipt_gate
+
+        c = case(2, steps=3200)
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp)
+            receipt = path / f"re{c['re_d']}_s2.json"
+            with self.assertRaisesRegex(ValueError, "No sibling run receipt"):
+                receipt_gate(path, c)
+            for fields, message in (
+                (dict(run_status="INCOMPLETE"), "INCOMPLETE"),
+                (dict(run_status="INVALID_SOURCE_CHANGED", source_recheck="CHANGED"), "INVALID"),
+                (dict(run_status="COMPLETE", source_recheck="RECHECK_FAILED"), "RECHECK_FAILED"),
+                (dict(run_status="COMPLETE"), "source_recheck=None"),
+                (dict(), "Legacy run receipt"),
+            ):
+                receipt.write_text(json.dumps(dict(case=c, **fields)))
+                with self.assertRaisesRegex(ValueError, message):
+                    receipt_gate(path, c)
+            receipt.write_text(json.dumps(dict(case=dict(c, scale=1), run_status="COMPLETE",
+                                               source_recheck="UNCHANGED")))
+            with self.assertRaisesRegex(ValueError, "different case"):
+                receipt_gate(path, c)
+            receipt.write_text(json.dumps(dict(case=c)))
+            self.assertEqual(receipt_gate(path, c, legacy=True), "LEGACY_NO_FINAL_SOURCE_RECHECK")
+            receipt.write_text(json.dumps(dict(case=c, run_status="INCOMPLETE")))
+            with self.assertRaisesRegex(ValueError, "INCOMPLETE"):
+                receipt_gate(path, c, legacy=True)  # legacy opt-in never admits new statuses
+
+
 if __name__ == "__main__":
     unittest.main()