ext-mysql2: connection from pool.getConnection() throws 'Invalid connection handle' on beginTransaction/execute

[proggeramlug]

Env: perry 0.5.1512 built from main@6173ff9f6, macOS arm64, MySQL 8.0.46. MB24 Phase-0 spike.

Repro:

import mysql from "mysql2/promise";
const pool = mysql.createPool({ /* env */ });
const c = await pool.getConnection();   // resolves fine; c.release() alone works
await c.beginTransaction();             // throws

Actual: thrown value is the plain string "Invalid connection handle" (see also the separate errors-as-strings issue). Methods on the checked-out connection (beginTransaction, execute) don't see a valid underlying handle.

Expected: the mysql2 PoolConnection API — getConnection() → beginTransaction() → execute("SELECT … FOR UPDATE") → commit()/rollback() → release().

Impact: this is the canonical row-lock transaction pattern (SELECT … FOR UPDATE), i.e. the serialization backbone for anything auction/ledger-shaped; there is currently no way to run an explicit transaction from a pool under Perry. createConnection()-based transactions could not be verified either (session cut short by the param-binding race, filed separately).

[proggeramlug]

Closed by #8765, landed on main via #8778 (squash 1f5c3bb80).

That PR was landed through a batch wrapper PR rather than merged directly, so GitHub's close keyword never fired at merge time — its mergedAt is null even though the work is on main. Verified before closing: changelog.d/8765-mysql2-request-scoped-statements.md is present and perry-ext-mysql2 --lib passes 10/10 on the merged result.