MEM-027: patch_walk unbounded BASS carving exhausts the arena (sniff/PATCH.c)

Recursive patch_walk a_carves ~29MB per directory level (3×4MB trees + 16MB blob + entry arrays) and recurses into every subdir with no depth bound; the plain recursive call keeps each parent's carve live for the whole subtree, so a tree ~34 levels deep overflows the 1GB ABC_BASS. The leaf loop also issues (void)fetch_blob / (void)GRAFMerge3Bytes / (void)GRAFMergeWtFileTunable as plain calls, so any callee BASS scratch is never rewound per iteration and accumulates with file count. a_carve returns BNOROOM (graceful, no OOB), so this is resource exhaustion that fails deep/large trees unpredictably. The goal is to bound depth and reclaim per-leaf scratch.

Issues

Per-level carve held across recursion; per-leaf scratch never rewound.

Blockers

None.

Planned

Bound depth; rewind per leaf.