* feat(core): add dynamic swarm worker tool
Add a swarm tool for ad-hoc parallel worker execution with bounded concurrency, wait-all and first-success modes, per-worker failure
isolation, and aggregated results.
Register the tool in core, prevent nested worker recursion, and document the new workflow.
* fix(core): harden swarm worker execution
Prevent swarm calls from bypassing the outer scheduler concurrency budget.
Disallow interactive question prompts in swarm workers by default, and avoid incomplete Markdown table escaping by using an HTML entity for
pipe characters. Add focused tests for the scheduler behavior, worker tool restrictions, and result formatting.