fix: pre-merge review — Python yaml ledger + spec doc Java section

Two non-blocking review findings from the FR5a fixture-migration review:

- Python yaml drift gating was an inline set in test_yaml_conformance.py.
  Extracted to a sibling yaml-conformance-expected-failures.json ledger
  file matching the C# / Java pattern. Single source of truth; easier
  to audit. Drift summary preserved in the ledger's _drifts field.

- spec/conformance-tests.md still described the Java conformance runner
  as "(in progress, H3b)" with a hypothetical path. Java shipped fully
  green long ago; updated the section to describe the live runner at
  server/java/metadata/src/test/java/com/metaobjects/conformance/ConformanceTest.java.

Python conformance: 94/94 still green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dmealing

server/python/tests/conformance/test_yaml_conformance.py

@@ -105,15 +105,17 @@ def _discover() -> list[YamlFixture]:
 
 _FIXTURES = _discover()
 
-# FR5a envelope-shape gates — fixtures where Python's emitted source differs from
-# TS's (the FR5a reference port) by more than the jsonPath alone. Listed here so
-# the YAML conformance suite stays green; per-port reconciliation tracked in the
-# FR5a follow-up. Each entry MUST be accompanied by the drift summary.
-_FR5A_ENVELOPE_DRIFT_FIXTURES = {
-    # Python threads source one level deeper, to the offending @attr; TS stops
-    # at the parent object.entity.
-    "error-yaml-reserved-as-attr",
-}
+# FR5a envelope-shape gates — sourced from a sibling ledger file (matching the
+# C# / Java pattern). Each entry is a known cross-port drift where Python's
+# emitted source field differs from TS's (the FR5a reference port) by more
+# than the jsonPath alone. The code-set check still runs; only the full-envelope
+# assertion is skipped. Reconcile per the FR5a follow-up.
+_LEDGER_PATH = Path(__file__).parent / "yaml-conformance-expected-failures.json"
+_FR5A_ENVELOPE_DRIFT_FIXTURES = (
+    set(json.loads(_LEDGER_PATH.read_text(encoding="utf-8")).get("fixtures", []))
+    if _LEDGER_PATH.exists()
+    else set()
+)
 
 
 def _load_yaml_to_canonical(yaml_text: str) -> tuple[str, list[str], list[MetaError], list[str]]:

server/python/tests/conformance/yaml-conformance-expected-failures.json

@@ -0,0 +1,10 @@
+{
+  "language": "python",
+  "_comment": "FR5a envelope-shape gate: Python's emitted source field differs from TS (the FR5a reference port) for these YAML fixtures. The code-set check still runs; only the full-envelope assertion is skipped. Each entry MUST be accompanied by the drift summary below. Reconcile per the FR5a follow-up — make Python's error-construction sites emit the same canonical jsonPath TS does.",
+  "fixtures": [
+    "error-yaml-reserved-as-attr"
+  ],
+  "_drifts": {
+    "error-yaml-reserved-as-attr": "Python threads source one level deeper, to the offending @attr; TS stops at the parent object.entity."
+  }
+}

spec/conformance-tests.md

@@ -156,13 +156,12 @@ directory, same canonical output. Auto-discovers fixtures from
 produces a different canonical string for any fixture, that's a bug in C#'s Loader or
 serializer — not in the fixture.
 
-## Java conformance runner (in progress, H3b)
+## Java conformance runner
 
-Same algorithm. H3a (loader-restructure) shipped 2026-05-19; H3b (conformance harness) is
-in progress. Will live at `java/<module>/src/test/java/com/metaobjects/ConformanceTest.java`.
-Same fixtures, same canonical output. If the Java implementation produces a different
-canonical string for any fixture, that's a bug in Java's Loader or serializer — not in the
-fixture.
+Lives at `server/java/metadata/src/test/java/com/metaobjects/conformance/ConformanceTest.java`
+and runs via `mvn -pl metadata test`. Same fixture directory, same canonical output.
+If the Java implementation produces a different canonical string for any fixture,
+that's a bug in Java's Loader or serializer — not in the fixture.
 
 ## Adding a new fixture