Resolves three execution-proven verifier findings from the scaffold review.
Full suite: 548 passed, 1 skipped (stable across repeated runs); ruff clean.
builders denylist (§3.3.2 #2): scan was +++-only and missed header-only
sections. Now section-driven off `diff --git a/<src> b/<dest>`, catching the 4
proven bypasses — delete of a denied path, mode-change-only, `copy to` a denied
path, out-of-scope delete (regression tests for each).
§3.3.1 compare-and-set concurrency: BEGIN IMMEDIATE moved inside guarded retry;
each CAS now runs on its own connection (shared sqlite3.Connection cannot hold
two transactions, and is unsafe for concurrent use even for reads). connect()
stashes the db path on a Connection subclass so the path is derived by a
thread-safe attribute read, not a PRAGMA on the shared conn; busy_timeout set
before the WAL pragma. Added shared-connection concurrent regression tests
(distinct + same question) — previously raised "transaction within a
transaction".
operator CLI (run-team.py): added the design-named re-deliver and force-resume
verbs (were missing); audit now records the attempt BEFORE the mutation and the
outcome after, so a ledger mutation can never land without a trail; main()
catches OSError instead of leaving an uncaught traceback on audit-write failure.
