fix(kvb-check-gate): skip parent journal rows whose text cannot be encoded

A row with a lone surrogate in gate-parents.jsonl, which sandboxed agents can write, raised UnicodeEncodeError at the TEMP table insert and crashed every commit-msg, pre-push and pre-merge-commit hook and the hub gate view. opened() now keeps only rows whose repo, branch and parent encode; the test fails without the change.

🎯 Fix: 97 %
💥 Break: 2 %
💸 Cost: 100 %
⏱️ Time: 100 %
🛡️ Security: 100 %
🏆 Score: 95
🚦 Gate: ✅ 90/5, cost and time <= 100, security 100 %

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

tests/test_gates.py

@@ -139,6 +139,12 @@ class TestGates(Scratch):
         check = self.gates("receipt", "check", "--repo", repo, "--tree", tree, "--level", "test")
         self.assertEqual((check.returncode, check.stderr), (0, ""))
 
+    def test_a_parent_row_with_a_lone_surrogate_is_skipped_and_the_others_still_count(self):
+        self.council.mkdir(exist_ok=True)
+        rows = [{"id": "bad", "repo": str(self.repo), "branch": "main", "parent": "\ud800"}, {"id": "good", "repo": str(self.repo), "branch": "main", "parent": "feature"}]
+        (self.council / "gate-parents.jsonl").write_text("".join(json.dumps(row) + "\n" for row in rows), encoding="utf-8")
+        self.assertEqual(self.parents("main"), [{"parent": "feature", "source": "recorded"}])
+
     def test_a_receipt_older_than_30_days_neither_counts_nor_survives_the_next_write(self):
         repo, tree = str(self.repo), self.out("rev-parse", "HEAD^{tree}")
         old = {"id": "old", "repo": repo, "tree": tree, "level": "test", "gpu": "false", "at": time.time() - 31 * 86400}