ADR-021: third review round — tx-read methods, Job.claimed_at, schedule() queue validation, drop=rollback, receiver arms

docs/architecture/decisions/007-transactional-seam.md

@@ -35,6 +35,13 @@ handle.commit() / handle.rollback()
   `*_tx` operation lands in *the caller's transaction*; commit/rollback
   are explicit and owned by the caller. Non-`_tx` operations are the
   auto-commit convenience counterparts, each atomic alone.
+  *(Drop disposition pinned 2026-10-07 by
+  [ADR-021](021-tx-reads-and-value-shape-fixes.md) §4: a handle
+  dropped without `commit`/`rollback` rolls back — the no-ghosts
+  property holds through RAII paths, not only the explicit ones;
+  SQLite's writer-slot lease releases with the rollback, the pg
+  pooled client rolls back and re-pools; honker's documented
+  `Transaction` `Drop` behavior is the inherited precedent.)*
 - **Postgres** ([ADR-004]): the handle holds the pooled connection
   object directly (tokio-postgres `Client` is `Send + Sync` — verified
   by a compile-time probe). Straight `.await`s, no bridge, no hop