fix(runtime): surface agent_call middleware bypass on sync agent methods

[Atharva-Kanherkar]

refs #114

agent_call middleware is documented as wrapping the entire agent method, but it only wraps traced async methods. sync methods, @no_trace methods (sync or async), staticmethod/classmethod, and methods inherited from non-Agent bases all run outside it, so a registered guard silently does not apply.

no behaviour change. this warns instead of staying silent, and fixes the docs that promised full coverage.

real gpt-5-mini run of the reproducer from #114, on this branch:

repro_114_real.py:45: RuntimeWarning: agent_call middleware is registered, but it
does not apply to these methods on PaymentAgent: charge_card. Middleware is async
and only wraps async agent methods that the metaclass instruments, so synchronous
methods, @no_trace methods, staticmethod/classmethod, and methods inherited from
non-Agent bases all execute outside it. Guards that block, authenticate, or
rate-limit will not run for them - including when generated CodeAct Python calls
them. Declare such a capability as a traced 'async def' method to bring it under
middleware, or enforce the policy inside the method body.
  result = await agent.perform()

{'result': 'done', 'charges': [100], 'intercepted_methods': ['perform']}

same result as the issue, but the gap is now reported at await agent.perform(), before the model reaches charge_card.

changes:

• warn once per class, naming every uncovered method, when middleware is registered
• correct the docs in middleware.py, event_manager.py, the middleware skill, and the relay example
• tests for the asymmetry, each uncovered kind, both delivery paths, and -W error

6263 passed, 152 skipped. tests/test_mcp excluded, optional dep not installed here. ruff and format clean.

open question: should this raise instead of warn? and @no_trace async bypassing middleware may be worth its own issue, since one decorator is controlling both tracing and policy.