Deprecate McpErrorCode.ResourceNotFound (-32002) and use McpErrorCode.InvalidParams (-32602) per SEP-2164

[jayaraman-venkatesan]

Fixes #1540

SEP-2164 standardizes the error code for "resource not found" from the MCP-specific -32002 to the standard JSON-RPC -32602 (Invalid Params), as part of the 2026-06-30 MCP spec release.

How Has This Been Tested?

• Existing test suite passes locally (dotnet test) — no new tests were needed since the existing resource routing, resource builder, and exception propagation tests already cover the error code path; their assertions were updated to expect -32602.

Breaking Changes

McpErrorCode.ResourceNotFound is marked [Obsolete] but retained at its original value -32002 for backward compatibility with pre-2026-06-30 clients and servers that may still send or check for that code. New code should use McpErrorCode.InvalidParams (-32602).

Server implementors who currently throw McpErrorCode.ResourceNotFound will see a compiler warning directing them to migrate to McpErrorCode.InvalidParams.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

• McpErrorCode.ResourceNotFound = -32002 is marked [Obsolete] with a message pointing to InvalidParams
• The default ReadResource handler in McpServerImpl now throws InvalidParams
• McpErrorCode.InvalidParams docs updated to list Resources as a covered context
• All internal usages (server, test servers, tests) migrated to InvalidParams