PgSQL Poisoned-Query ASAN UAF Implementation Plan

Goal: Keep the incoming simple-query packet alive until request logging and parser cleanup finish, then verify the complete ASAN TAP fan-out on PR #6083.

Design: CurrentQuery borrows its SQL pointer from the packet handled by handler_poisoned_simple_query(). Preserve the existing ownership model and move RequestEnd() before l_free() in both exits; do not add a copy or change mirror-session behavior.

Implementation

1. Use the existing failing ASAN run of pgsql-retry_guard_in_txn_on_broken_backend-t as the regression's red state.
2. Reorder finalization and packet release in both malformed and normal exits.
3. Run formatting/diff checks and focused source checks, then commit and push ci/verify-asan-label so the label-selected ASAN workflow reruns.
4. Inspect all prior failed PR #6083 jobs, group failures by sanitizer signature, and compare them against the fresh run before making any additional fix.