feat: add logging conformance scenarios (capability, invalid level, threshold filtering)

[elang2]

Summary

Adds three new conformance scenarios for the logging/setLevel endpoint (issue #435):

1. logging-capability-advertisement — verifies the server advertises capabilities.logging in its initialize response
2. logging-invalid-level — verifies the server rejects unrecognized severity levels (e.g. "banana") with -32602 (Invalid Params)
3. logging-threshold-filtering — verifies that notifications/message respects the configured severity threshold (suppresses below, allows above)

Scenarios 2 and 3 are registered in pendingClientScenariosList because the everything-server does not implement invalid-level rejection or threshold-based filtering. They can be run targeted against a compliant fixture server via npm start -- server --scenario logging-invalid-level --url <fixture>.

Scenario 1 is in the active list and passes against the everything-server.

Spec references

• https://modelcontextprotocol.io/specification/2025-11-25/server/utilities/logging

Test plan

• npm run build passes
• logging-capability-advertisement passes against everything-server
• logging-invalid-level correctly skipped (pending) in default suite
• logging-threshold-filtering correctly skipped (pending) in default suite

Closes #435

[elang2]

@joy7758 would appreciate your review on this one when you get a chance.

[joy7758]

Thanks for the follow-up. I reviewed current head 79acb3987aec6ca0acf32264abbfeba250c0779f. I am not proposing a competing implementation.

I found four scope/evidence points worth resolving before these checks are treated as conformance results:

1. Threshold filtering does not currently have RFC-keyword backing. logging.ts:L256-L262 labels suppression as MUST NOT and emission at debug as SHOULD. The cited 2025-11-25 logging page says clients MAY send logging/setLevel, but I cannot find either receiver requirement there. Unless there is another normative sentence to cite, these should be treated as a non-scoring interoperability observation or an upstream spec gap, not enforced as protocol conformance.

2. Capability advertisement is conditional. logging.ts:L71-L95 warns whenever capabilities.logging is absent. The spec requires that capability only for a server that emits log notifications. A server that does not implement logging can therefore be compliant. This check needs either evidence that the server emits/supports logging or a non-scoring outcome when the feature is not claimed.

3. Zero notifications should not silently become a neutral result after the fixture contract is invoked. logging.ts:L293-L305 returns SKIPPED. If test_tool_with_logging is a controlled prerequisite that promises at least an error-level sentinel, zero notifications means the prerequisite/evidence path failed, so the threshold was not tested. I would use the suite's explicit inconclusive/prerequisite-failure convention rather than SKIPPED; if the server is allowed to emit nothing, this behavior is simply unobservable and should not be scored.

4. The invalid-value probe still needs wire evidence. Registering it as pending keeps it out of the default suite, but does not by itself show that a targeted run avoids wire-schema-harness-error. Please include the targeted checks.json/wire-schema output for the intentionally invalid request.

The repository contribution guide also asks for a passing real-SDK run and a specific failing case. The PR currently documents the in-repo everything-server path, so adding the pinned real-SDK output plus a negative fixture/result would complete the evidence loop.

The -32602 handling itself is correctly scoped as a SHOULD. No protocol change is being suggested here.

[elang2]

Thanks @joy7758, all four points are valid. I'll push a revision that:

• Downgrades threshold filtering to non-scoring (no normative backing in the spec)
• Makes the capability check conditional on evidence of logging support
• Uses untestableCheck() for the zero-notification case
• Adds wire evidence for the invalid-level probe

[elang2]

All four points from @joy7758 addressed and pushed. Threshold filtering is non-scoring now, capability check probes for logging support first, zero-notification uses untestableCheck(), and wire evidence added for invalid level.

Maintainer review welcome when someone has time.