feat(vmcp): add support for ResourceLink content type

[Sanskarzz]

Summary

This PR implements support for the ResourceLink content type (type discriminant "resource_link") in the vMCP bridge layer. Previously, ResourceLink content returned by backend MCP servers was unrecognized by the conversion layer, causing it to fall through to "unknown" and eventually be emitted as empty text, losing critical resource pointers and metadata.

Key Changes

• Core Types: Extended vmcp.Content in pkg/vmcp/types.go to include Name and Description fields, allowing it to faithfully represent a ResourceLink .
• Conversion Layer: Added contentTypeLink constant to pkg/vmcp/conversion/content.go. Updated ConvertMCPContent to detect mcp.ResourceLink via type assertion and map it to vmcp.Content. Updated ToMCPContent to reconstruct mcp.ResourceLink using mcp.NewResourceLink.
• Tests: Added new test cases to TestConvertMCPContent and TestToMCPContent in conversion_test.go. Added TestResourceLinkRoundTrip to verify that data is preserved when converting in both directions.

Validation Results

All tests in pkg/vmcp/conversion and pkg/vmcp/server/adapter pass. go vet is clean.

Fixes #3960

[codecov]

Codecov Report

❌ Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 68.64%. Comparing base (0791876) to head (d427091).

Files with missing lines	Patch %	Lines
pkg/vmcp/conversion/content.go	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4023      +/-   ##
==========================================
+ Coverage   68.62%   68.64%   +0.01%     
==========================================
  Files         445      445              
  Lines       45374    45385      +11     
==========================================
+ Hits        31140    31154      +14     
+ Misses      11827    11826       -1     
+ Partials     2407     2405       -2     

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[jerm-dro]

Hey @Sanskarzz thanks for the PR. I notice "[WIP]" in the PR description. Is this ready for review?

[jerm-dro]

Suggestion, non-blocking: we could make this a type. Then, we wouldn't have to repeatedly document the supported types. For example:

type SupportedContentType string

const (
   SupportedContentTypeText SupportedContentType = "text"
   // ... and so on
)

[Sanskarzz]

I've added ContentType as a string alias and updated all affected test files (including integration tests) to ensure type safety and consistency.

[Sanskarzz]

Hey @Sanskarzz thanks for the PR. I notice "[WIP]" in the PR description. Is this ready for review?

Apologies, my bad. The PR is ready to review.