Bash and memory sync now block bulk deletion of synced memory files

What

• A new check (massDeleteHoldExposure) blocks removing memory files when doing so would exceed a threshold of missing-or-targeted synced files at once, returning a refusal message that asks you to wait about a minute for sync to catch up.
• A new method on the memory-store manager computes this "hold exposure" across both the shared multi-store and the user multi-store whenever a mass delete is requested.
• The Bash tool's input validation now also runs this check asynchronously, after its existing checks, as part of deciding whether a command is allowed.
• Specifically, Bash's validation scans rm commands for literal delete targets and calls this memory-store check; if a command would remove more synced memory files than the threshold allows at once, it's refused with an explanatory error instead of being allowed to run.

Why

This prevents a single rm command (or other mass-delete action) from wiping out more synced memory files than the sync process can safely account for, avoiding data loss or inconsistent state while sync catches up.