Spec corrections & deprecation markers

[maxisbey]

Tracks: #2794 #2805

Small corrections plus the deprecation markers required by the lifecycle policy.

What's in it

• Server emits -32602 (with data.uri) for unknown resources; client accepts both old and new (SEP-2164).
• A shared "deprecated per spec" helper (SEP reference + earliest-removal date in the warning).
• Apply markers to: HTTP+SSE transport, includeContext values, roots/sampling/logging surfaces, the legacy dynamic-client-registration fallback (per SEP-2596).

Conformance

• sep-2164-resource-not-found

Dependencies

• Depends on: none

References

• SEP-2164
• SEP-2577
• SEP-2596
• Deprecated features

[maxisbey]

Done via #2920 and #2926 (error-code corrections + SEP-2577 deprecation markers).

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