fix(sp38): restore per-kind control_number in find_ack_orphans + review cleanups

Three pr-reviewer followups from the 2026-07-07 review of commit ad14b56:

1. BUG: find_ack_orphans refactor routed 277ca/ta1 through
   _ack_control_number which only knew 999 — restored per-kind source
   (999 reads raw_json.envelope.control_number, 277ca/ta1 read the ORM
   control_number column). Added regression test pinning all three
   kinds.

2. DOCSTRING DRIFT: reconcile_orphan_st02s said 'remaining columns
   take their defaults' but explicitly passes parsed_at and
   transaction_set_control_number — added both to the explicit list
   and clarified the rest take schema defaults.

3. WASTED SORT: _iter_orphan_999_st02s yielded sorted() but the
   caller re-sorts by (-ack_count, st02) — yielding unsorted now.

Plus three cleanups the reviewer flagged:

* Hoisted 'json' / 'uuid' / 'datetime' imports to module top of
  store/__init__.py (replaced in-method imports).
* Added two missing tests: sentinel grep-discoverability via
  LIKE '<synthetic:%>' + 999-walk tolerance for non-dict raw_json
  (None / list shapes — bytes is unreachable through the ORM).
* Aligned spec/plan exit codes to the cyclone-cli convention
  (exit 1 on DB error, not 2 — matches the existing CLI
  sys.exit(1) and the cyclone-cli skill documentation).

36/36 SP38 tests pass.

backend/tests/test_apply_claim_ack_links.py

@@ -34,6 +34,7 @@ from cyclone.claim_acks import (
     lookup_claims_for_ack_set_response,
 )
 from cyclone.db import (
+    Ack,
     Batch,
     Claim,
     ClaimState,
@@ -744,6 +745,75 @@ def test_store_facade_exposes_claim_ack_methods():
         assert hasattr(store, name), f"missing CycloneStore.{name}"
 
 
+# ---------------------------------------------------------------------------
+# SP38 follow-up: regression test for the 277ca / ta1 control_number
+# behavior preserved across the find_ack_orphans refactor.
+# ---------------------------------------------------------------------------
+
+
+def test_find_ack_orphans_returns_control_number_for_all_kinds():
+    """For each ack kind, ``find_ack_orphans(kind)`` must return the
+    control_number from the per-kind source:
+
+      * 999 — from raw_json.envelope.control_number
+      * 277ca — from the ORM column ``control_number``
+      * ta1 — from the ORM column ``control_number``
+
+    Regression for sp38 commit ad14b56 which initially routed all
+    three kinds through _ack_control_number and broke 277ca/ta1
+    (the helper only knew 999). Found by pr-reviewer 2026-07-07.
+    """
+    import json
+    import cyclone.db as _db_mod
+    Two77caAck = _db_mod.Two77caAck
+    Ta1Ack = _db_mod.Ta1Ack
+    parsed_at = datetime.now(timezone.utc)
+
+    with db.SessionLocal()() as s:
+        # 999 orphan with envelope.control_number in raw_json
+        s.add(Ack(
+            source_batch_id="999-orph-test",
+            accepted_count=1, rejected_count=0, received_count=1,
+            ack_code="A",
+            parsed_at=parsed_at,
+            raw_json=json.dumps({
+                "envelope": {"control_number": "999-ctrl-num",
+                             "sender_id": "S", "receiver_id": "R",
+                             "transaction_date": "2024-01-01",
+                             "implementation_guide": "005010X231A1"},
+                "set_responses": [],
+                "summary": {},
+            }),
+        ))
+        # 277ca orphan with control_number in ORM column
+        s.add(Two77caAck(
+            source_batch_id="277ca-orph-test",
+            accepted_count=1, rejected_count=0,
+            control_number="277CA-CTRL-NUM",
+            parsed_at=parsed_at,
+        ))
+        # ta1 orphan with control_number in ORM column
+        s.add(Ta1Ack(
+            source_batch_id="ta1-orph-test",
+            ack_code="A",
+            control_number="TA1-CTRL-NUM",
+            parsed_at=parsed_at,
+        ))
+        s.commit()
+
+    orphans_999 = store.find_ack_orphans("999")
+    orphans_277ca = store.find_ack_orphans("277ca")
+    orphans_ta1 = store.find_ack_orphans("ta1")
+
+    ctrl_999 = [o["control_number"] for o in orphans_999 if "999-ctrl-num" in o["control_number"]]
+    ctrl_277ca = [o["control_number"] for o in orphans_277ca]
+    ctrl_ta1 = [o["control_number"] for o in orphans_ta1]
+
+    assert "999-ctrl-num" in ctrl_999, f"999 control_number not found: {ctrl_999}"
+    assert "277CA-CTRL-NUM" in ctrl_277ca, f"277ca control_number empty: {ctrl_277ca}"
+    assert "TA1-CTRL-NUM" in ctrl_ta1, f"ta1 control_number empty: {ctrl_ta1}"
+
+
 # ---------------------------------------------------------------------------
 # Step 2.1 — pure walk-through unit test (no DB) for the orphan tracking
 # ---------------------------------------------------------------------------