Add MCP registry details for awesome-copilot

[justinyoo]

Purpose

• Add MCP registry support for the awesome-copilot sample so it can be published to the Model Context Protocol registry.
• Introduce awesome-copilot/server.json with server metadata (name, description, version, OCI package reference).
• Update the build-container workflow to compute a date-based registry version, tag the awesome-copilot image with that version, and publish to the MCP registry using mcp-publisher.
• Add the io.modelcontextprotocol.server.name label to both awesome-copilot Dockerfiles.
• Add MCP registry token files to .gitignore.

Does this introduce a breaking change?

[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] New feature to existing sample
[ ] New sample
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

README updated?

[ ] No
[x] N/A

How to Test

• Get the code

cd mcp-dotnet-samples
git checkout feat/registry

• Test the code

cat awesome-copilot/server.json | python -m json.tool

# Verify Dockerfile labels
grep -n 'io.modelcontextprotocol' Dockerfile.awesome-copilot Dockerfile.awesome-copilot-azure

What to Check

Verify that the following are valid

• awesome-copilot/server.json contains correct server name, description, repository URL, and OCI package identifier
• The build-container workflow conditionally applies registry steps only for awesome-copilot
• Both Dockerfiles include the io.modelcontextprotocol.server.name label
• .gitignore includes MCP registry token files

Other Information

The MCP registry publish steps use GitHub OIDC for authentication and only run for the awesome-copilot image.