test(rank): pin language_gate/language_note contract in the /rank spec (#278)

Follow-up suggested during PR #275's merge review: spec-pinning tests for
the language_gate/language_note fields, matching the pattern already used
for the sibling gaps/strengths fields in this same file.

Four new assertions: Step 2's scoring-agent JSON schema declares both
fields with the PASS/FAIL/FLAG enum and distinguishes them from the
pre-existing `language` field; Step 3 documents the Language veto rule
mirroring the existing Location veto; Step 4 persists both fields into
seen_jobs.json; Step 5's presentation rules document the FLAG marker.

The Step 4 persistence test is a real regression guard, not just
documentation: language_gate/language_note were computed in Step 2 and
used to decide Step 3's veto, but an earlier version of this spec never
instructed Step 4 to actually write them to seen_jobs.json - caught via
live debugging (a real /rank run showed language_gate: null on every
entry despite the run reporting genuine vetoes), fixed once already.
Verified live that this test fails against that exact regression and
passes against the current (fixed) spec text.

tests/test_rank_command.py

@@ -78,6 +78,72 @@ class RankCommandSpec(unittest.TestCase):
             "schema note must say old entries lacking strengths/gaps are tolerated, never backfilled",
         )
 
+    def test_step2_schema_includes_language_gate_fields(self):
+        sections = _sections(COMMAND.read_text(encoding="utf-8"))
+        step2 = sections.get("Step 2: Batch-Fetch and Score", "")
+        self.assertIn('"language_gate"', step2, "Step 2's scoring-agent JSON must include language_gate")
+        self.assertIn('"language_note"', step2, "Step 2's scoring-agent JSON must include language_note")
+        self.assertIn(
+            '"PASS" | "FAIL" | "FLAG"',
+            step2,
+            "language_gate must use the same PASS/FAIL/FLAG verdict set as the location veto",
+        )
+        self.assertIn(
+            "distinct from",
+            step2,
+            "spec must distinguish language_gate/language_note from the pre-existing 'language' field "
+            "(which records the posting's own language, not a veto verdict) - the two are easy to conflate",
+        )
+
+    def test_step3_documents_language_veto(self):
+        sections = _sections(COMMAND.read_text(encoding="utf-8"))
+        step3 = sections.get("Step 3: Aggregate and Rank", "")
+        self.assertIn(
+            "Language veto",
+            step3,
+            "Step 3 must document a Language veto rule, mirroring the existing Location veto",
+        )
+        self.assertIn(
+            "excludes the job from the shortlist",
+            step3,
+            "a language_gate FAIL must be documented as excluding the job, same as a location FAIL",
+        )
+
+    def test_step4_persists_language_gate_and_language_note(self):
+        """Regression guard: language_gate/language_note were computed in Step 2 and used
+        to decide Step 3's veto, but never written to seen_jobs.json - live-debugged and
+        fixed once already (a real /rank run showed language_gate: null on every entry
+        despite the run reporting real vetoes). This pins the fix in the spec text the
+        same way test_step4_persists_gaps_and_strengths pins the sibling strengths/gaps
+        persistence bug, so a future edit can't silently reintroduce either loss.
+        """
+        sections = _sections(COMMAND.read_text(encoding="utf-8"))
+        step4 = sections.get("Step 4: Update State", "")
+        self.assertIn('"language_gate"', step4, "Step 4 must persist language_gate into seen_jobs.json")
+        self.assertIn('"language_note"', step4, "Step 4 must persist language_note into seen_jobs.json")
+        self.assertIn(
+            "as important to persist as the score itself",
+            step4,
+            "Step 4 must call out that the veto fields (location/language_gate/language_note) are not optional extras",
+        )
+
+    def test_step5_documents_language_flag_marker(self):
+        # Note: _sections() splits on every "\n## " line, including the "## Job
+        # Ranking - YYYY-MM-DD" line inside Step 5's own fenced example template -
+        # so the presentation rules that follow that example live under that key,
+        # not "Step 5: Present the Shortlist" itself. Matches how the existing
+        # gaps/strengths tests above only probe Step 4, never Step 5, for the same
+        # reason - documented here since it's easy to trip over when adding a new
+        # Step-5-content test.
+        sections = _sections(COMMAND.read_text(encoding="utf-8"))
+        step5_rules = sections.get("Job Ranking - YYYY-MM-DD", "")
+        self.assertIn(
+            "language_gate: FLAG",
+            step5_rules,
+            "Step 5's presentation rules must document the ⚠ marker + language_note callout "
+            "for a shortlisted FLAG job, mirroring the existing location FLAG treatment",
+        )
+
     @unittest.skipUnless(
         _HAVE_YAML,
         "PyYAML not installed (the CI Python-test job omits it; the lint job runs lint_skills.py directly)",