[FEATURE] Race-condition safe variables for workflow debounce #2918
Description
Summary
Need race-condition safe, cross-run variables (or built-in debounce/lock) for webhook bursts.
Problem
Workflow variables are per-run only, so concurrent executions cannot coordinate. This makes debounce/“latest message wins” logic unreliable.
Current behavior
Multiple webhook runs triggered within seconds all proceed because each run sees only its own variable state.
Proposal
Add a persistent, atomic variable store scoped to workflow (optionally per-conversation) with compare-and-set semantics, or a built-in debounce/lock block with TTL.
Use case
User sends 4–5 messages quickly; only the latest run should continue after a wait window.