After rebasing onto develop, movePage runs its cycle-check + UPDATE inside
executeTx(this.db) (develop #207 advisory-lock/atomic cycle-guard). The
git-sync provenance specs still passed a bare `{}` db, so executeTx hit
`db.transaction is not a function`. Reuse the same trxStub Proxy + transaction
mock the develop movePage specs use so both the advisory-lock `sql.execute(trx)`
and updatePage resolve. Production movePage keeps BOTH develop's lock/cycle
guard AND git-sync's provenance stamping; this only updates the test harness.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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