test: current-checkout mode for the projected-pair TG runner and assessor

run_case --current-checkout records the clean checkout (HEAD, src
fingerprint, harness hashes, pinned build-capture helper) labelled
current_checkout instead of requiring the frozen a135252 tree; receipts
carry numerical_revision=None. assess --current-checkout applies the same
gates to such receipts. Frozen mode is unchanged and now rejects any
receipt with source_mode, so the two never cross-qualify. A missing a135252
object is reported as unavailable history instead of a source diff.
check_projected_pairs.py is untouched, so its pinned hash and existing
receipts keep their meaning.

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

tests/validation/taylor_green/run_case.py

@@ -64,8 +64,16 @@ def provenance(repo):
     )
 
 
-def verify_source(repo, revision):
-    """Exact clean harness commit, fixed production tree, and reviewed capture helper."""
+CURRENT_CAPTURE = "current checkout, not the frozen a135252 qualification"
+
+
+def verify_source(repo, revision, current=False):
+    """Exact clean harness commit, fixed production tree, and reviewed capture helper.
+
+    current=True records the clean checkout itself instead of requiring the frozen
+    numerical tree; such receipts carry source_mode="current_checkout" and are only
+    assessed with assess(..., current=True), never as the frozen qualification.
+    """
     import oracle
     from tests.validation.multigrid import check_projected_pairs as gate
 
@@ -77,6 +85,17 @@ def verify_source(repo, revision):
     if (Path(gate.__file__).resolve() != helper
             or hashlib.sha256(helper.read_bytes()).hexdigest() != BUILD_CAPTURE_SHA256):
         raise RuntimeError("Wrong build-capture helper")
+    if current:
+        result = provenance(repo)
+        if result["revision"] != revision or result["dirty"]:
+            raise ValueError("requires the exact expected clean checkout")
+        result.update(source_mode="current_checkout", source_capture=CURRENT_CAPTURE,
+                      build_capture_sha256=BUILD_CAPTURE_SHA256)
+        return result
+    if subprocess.run(["git", "-C", str(repo), "cat-file", "-e", f"{NUMERICAL_REVISION}^{{commit}}"],
+                      capture_output=True).returncode:
+        raise RuntimeError(f"frozen numerical revision {NUMERICAL_REVISION} is not available "
+                           "in this clone; the frozen qualification cannot be checked")
     if gate.preflight(repo, revision, "candidate") != NUMERICAL_REVISION:
         raise RuntimeError("Wrong production revision")
     result = provenance(repo)
@@ -149,6 +168,8 @@ def main():
     p.add_argument("--depth", type=int, choices=[1, 2, 3], required=True)
     p.add_argument("--output", type=Path, required=True)
     p.add_argument("--explosion", choices=["constant", "projected_linear"], default="constant")
+    p.add_argument("--current-checkout", action="store_true",
+                   help="record the clean current checkout instead of the frozen a135252 tree")
     p.add_argument("--early-pressure", action="store_true",
                    help="also save 65 scalar pressure samples at t*=k*.001875, k=0..64")
     args = p.parse_args()
@@ -161,7 +182,7 @@ def main():
         p.error("--run-gpu and exactly one explicit CUDA_VISIBLE_DEVICES are required")
     repo = args.repo.resolve()
     sys.path[:0] = [str(repo / "src"), str(repo)]
-    source = verify_source(repo, args.expected_revision)
+    source = verify_source(repo, args.expected_revision, current=args.current_checkout)
     runtime = runtime_source(repo)
     if args.dry_run:
         print(json.dumps(dict(source=source, runtime_source=runtime, dry_run=True)))
@@ -182,7 +203,8 @@ def main():
     report = dict(
         schema=1,
         source=source,
-        numerical_revision=NUMERICAL_REVISION,
+        numerical_revision=None if args.current_checkout else NUMERICAL_REVISION,
+        **({"source_mode": "current_checkout"} if args.current_checkout else {}),
         reference_harness=REFERENCE_HARNESS,
         actual_build_sidecars=[],
         runtime_identity=None,