Add runtime policy guard for max tool calls per task

[David-patrick-chuks-02]

Description

Add a runtime policy guard that rejects or stops tasks exceeding a maximum number of tool calls.

Acceptance Criteria

• Configurable max tool calls per task
• Guard triggers typed runtime error when exceeded
• Unit tests cover under-limit and over-limit cases

Technical Notes

• Place logic near existing runtime guards
• Keep defaults conservative and documented

Labels

enhancement good first issue