Reproducer for MDEV-41450 (purge coordinator BF-aborted by Galera TOI DDL,
purge_sys_t::close_and_reopen() leaks THD mem_root).

Requirements: Docker, Python 3. Everything runs in disposable local containers.

  PROBE_IMAGE=mariadb:12.3.3 PROBE_LABEL=12.3.3 python3 local-purge-galera-probe.py

Other images: mariadb:11.4 (11.4.13, reproduces), mariadb:10.11.16 (purge THD
killed, no leak), mariadb:10.6 (not affected). PROBE_TV_KIND=stored runs the
STORED-column control (no leak).

The script starts a 2-node Galera cluster, creates a table with an indexed
VIRTUAL column plus 4 plain tables, builds a purge backlog behind a long read
view on node 2, then DROPs the plain tables via TOI on node 1 while node 2 is
purging, and samples RssAnon and memory/sql/THD::main_mem_root on node 2.
Output: local-purge-galera-<label>-samples.json and the node error logs.
