MEM-020: BROExec leaks mmap'd file (and keeper) on arena overflow (bro/BRO.exe.c)

Now
DONE

In BROExec's per-URI loop a file is FILEMapRO'd but only registered for cleanup (BRODefer b->maps) several lines later; between the two, call(u8bHost, b->arena, …) can return BNOROOM when the 128MB arena fills, and the call returns from BROExec before the mapping is recorded so BROClose (which iterates only b->maps) never unmaps it, and any open keeper teardown after the loop is skipped too. In an in-process be host this accumulates. The goal is to register the mapping before any returning call.

Issues

Mapping unregistered across a fallible call().

Blockers

None. Reached when the 128MB arena fills before all URIs are staged.

Planned

Acquire-then-register; teardown on every exit.