ToolRegistry.dispatch spread every injected keyword (task_id, session_id,
user_task, parent_agent, ...) into the handler, so a third-party plugin tool
written as `def handle(args)` raised TypeError on every call. The plugin
contract (plugins/AGENTS.md) says optional kwargs are signature-inspected, not
forwarded unconditionally; hooks already do this in plugins_dispatch. Handlers
taking **kwargs still receive the full payload. Docs updated: the narrow
signature is supported, **kwargs opts into the whole context.
Fixes#68318
credit: @vveerrgg #22146 (slim redo; #68636 is the later duplicate)
01eae47b3a