fix: standardize resource not found error code

[CrypticCortex]

Summary

• Align McpError.RESOURCE_NOT_FOUND with SEP-2164 by using JSON-RPC INVALID_PARAMS (-32602).
• Update the resource-not-found error code regression expectation.

Test plan

• ./mvnw -pl mcp-core -Dtest=McpErrorTest test
• ./mvnw -pl mcp-core test
• ./mvnw -pl mcp-core spring-javaformat:validate
• git diff --check

Closes #1001

[Kehrlann]

This is incorrect, now EVERY RESOURCE_NOT_FOUND usage will throw INVALID_PARAMS, even when it should be RESOURCE_NOT_FOUND, e.g. when a Resource does not exist

Additionally, this is a breaking change, unsure whether we will merge this before we create a 3.x branch.

[CrypticCortex]

Thanks, you’re right. change is too broad because it changes every RESOURCE_NOT_FOUND caller, including cases that should keep the existing resource-not-found code.

I prepared a narrower local fix: keep RESOURCE_NOT_FOUND = -32002, and only have the SDK-owned missing resources/read fallback return SEP-2164 INVALID_PARAMS (-32602) with data: { uri }, with tests for both behaviors.

Would you prefer that update now, or should this wait for 3.x / protocol-versioned behavior?

[Kehrlann]

Please apply it. I'll assign the original issue to you. Could you please comment on #1001 so I can assign you?

For when exactly we ship it, I'll keep you posted. Assigning to 3.x until we decide what to do.