Merge docs/phase2-stop-condition: Phase 2 Task 0 STOP condition resolved (does not fire)

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

docs/plans/2026-07-20-localdb-adoption-phase2.md

@@ -56,6 +56,29 @@ auth already in place, no in-memory SQLite in tests, cp-triplet-only rig inspect
    (**STOP condition:** a BLOB payload column cannot be registered — it must become base64 TEXT in
    the new schema, and the recon must size the largest realistic payload against the 171 KB-ish
    chunk guidance; alarm events are small JSON, so expect this to be fine, but verify).
+
+   > **PRE-ANSWERED 2026-07-21 (verified against `master` `d218282c`) — the STOP condition does NOT
+   > fire.** Re-verify cheaply during recon, but do not expect a surprise:
+   >
+   > - **Executed DDL:** `SqliteStoreAndForwardSink.cs:657-667`. It matches the class doc-comment at
+   >   `:17-26` exactly — no drift between the documented and executed schema.
+   > - **No BLOB.** All 8 columns are TEXT/INTEGER; the payload column is **`PayloadJson TEXT NOT
+   >   NULL`**. So no base64 conversion is needed and the chunk-size sizing is moot.
+   > - **Payload is small and bounded by shape.** `PayloadJson` is a serialized
+   >   `AlarmHistorianEvent` — 10 scalar fields (`AlarmId`, `EquipmentPath`, `AlarmName`,
+   >   `AlarmTypeName`, `Severity`, `EventKind`, `Message`, `User`, `Comment?`, `TimestampUtc`).
+   >   No collections, no nesting. Realistic worst case is low single-digit KB (operator `Comment`
+   >   is the only unbounded-ish field), far under the 171 KB chunk guidance.
+   > - **PK IS autoincrement** — `RowId INTEGER PRIMARY KEY AUTOINCREMENT`. This confirms the
+   >   plan's own prediction: LocalDb cannot replicate an autoincrement key, so the migrator
+   >   **must** mint deterministic `mig-{node}-{legacyId}` ids, and the new table needs a TEXT
+   >   GUID PK as already specified in the Architecture note.
+   > - **One index to carry across:** `IX_Queue_Drain ON Queue (DeadLettered, RowId)` (`:667`) —
+   >   the drain's covering index. The `alarm_sf_events` equivalent wants the same shape over
+   >   (dead-lettered flag, insertion order) so the drain query stays index-covered.
+   > - **Legacy column list for the migrator's `pragma_table_info` intersection check:**
+   >   `RowId, AlarmId, EnqueuedUtc, PayloadJson, AttemptCount, LastAttemptUtc, LastError,
+   >   DeadLettered`.
 2. The public seam: the interface the drain worker and producers use (e.g. `IAlarmHistorianSink` /
    enqueue+dequeue+markDelivered+deadLetter methods), so the rewire can keep it byte-compatible.
 3. Semantics to preserve: `Capacity` (1,000,000) enforcement, `MaxAttempts` (10), dead-letter