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.

docs/superpowers/plans/2026-07-07-cyclone-orphan-ack-housekeeping.md

@@ -127,8 +127,9 @@ assert the row count is unchanged after the second call.
 - [ ] `status` calls `cycl_store.find_ack_orphan_st02_summary()`,
       prints a table: `ST02 | ACK COUNT | HAS BATCH`. Total line at
       the bottom.
-- [ ] Exit 0 on success, exit 2 on DB error (matching `cyclone-cli`
-      convention).
+- [ ] Exit 0 on success, exit 1 on DB error (matching the
+      `cyclone-cli` convention: 1 = unexpected exception, including
+      SQLAlchemy DB errors).
 
 **RED test:** `tests/test_ack_orphans_cli.py::test_status_prints_table`
 using `CliRunner.invoke(["ack-orphans", "status"])`. Assert exit
@@ -142,7 +143,8 @@ line.
 - [ ] Calls `cycl_store.reconcile_orphan_st02s(dry_run=dry_run)`,
       prints `Created: N synthetic batch rows. Skipped: M (already
       had a batch row).`.
-- [ ] Exit 0 on success, exit 2 on DB error.
+- [ ] Exit 0 on success, exit 1 on DB error (same convention as
+      `status`).
 
 **RED test:** `tests/test_ack_orphans_cli.py::test_reconcile_creates_synthetic_batches`
 — seed two orphan ST02s (one with batch, one without), invoke