conformance: classify MCP spans before GenAI compatibility matching

[Utkarsh-Sinha0]

Summary

MCP spans may carry gen_ai.* compatibility attributes. If GenAI operation matching runs first, a valid MCP client or server span can be classified under the wrong registry entry, causing MCP-specific coverage to be lost.

This change:

• Classifies spans as mcp.client or mcp.server only when mcp.method.name, the corresponding span kind, and the resolved registry definition are present.
• Preserves existing GenAI fallback behavior for internal spans and registries without MCP definitions.
• Excludes only MCP-qualified samples from the three GenAI shape checks: span name, expected attributes, and span kind.
• Retains generic validation and unknown gen_ai.operation.name validation.
• Changes no registry definitions or registry pin.

Validation

• Coverage tests: 14 passed.
• Policy tests: 3 passed.
• Complete GenAI test suite: 19 passed with Weaver v0.25.1.
• Ruff: all checks passed.
• Pyright for the changed classifier source: 0 errors, 0 warnings.
• Diff whitespace validation: passed.

Any dependent semantic-conventions registry change remains separate.

Related: open-telemetry/semantic-conventions-genai#462

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[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Utkarsh-Sinha0 / name: Utkarsh Sinha (40d2610, dcd080d)

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