fix: accept wildcard patterns in Accept header per RFC 7231 §5.3.2

[VrtxOmega]

Added wildcard pattern matching to the Accept header parser. The server now correctly handles */*, type/*, and exact media type matches in order of specificity per the RFC.

Motivation and Context

The Streamable HTTP transport rejects requests with Accept: */* or Accept: application/* headers, returning an error instead of matching against supported media types. This violates RFC 7231 §5.3.2 which requires servers to honor wildcard Accept values.

Fixes #1641

How Has This Been Tested?

• Added tests for */* wildcard acceptance
• Added tests for application/* partial wildcard
• Added tests for exact match still working
• All 62 existing tests pass locally

Breaking Changes

None.

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

N/A