Context

Follow-up from PR #2473 (transactional ShellExecutor). Security audit identified that large files are copied without bounds during snapshot, risking disk exhaustion.

Proposed Change

Add max_snapshot_bytes: u64 to ShellConfig (default 0 = unlimited). Before copying each file in TransactionSnapshot::capture(), check cumulative snapshot size; abort with ToolError::SnapshotFailed if limit is exceeded.

[tools.shell]
transactional = true
max_snapshot_bytes = 104857600  # 100 MB

Priority

P3 — useful safety guard, not blocking for typical use cases.