<!-- Provide a brief summary of your changes -->
## Motivation and Context
Microsoft uses `mcr.microsoft.com` to host our public containers. These
are syndicated to Docker Hub but image references use
`mcr.microsoft.com` which is not currently supported by the Official MCP
Registry.
See https://github.com/modelcontextprotocol/registry/issues/753.
Microsoft teams want to use MCR-based images for Microsoft MCP servers.
I believe we should be adding ACR support as well, so that our customers
using Azure Container Registry can use the MCP Registry as well.
In short, MCR is used for Microsoft managed containers. ACR is a
solution for Azure customers to host their own containers.
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
Unit tests.
Manual test: local push of a server.json with
`mcr.microsoft.com/azure-sdk/azure-mcp:2.0.0-beta.1` and
`azurearcjumpstart.azurecr.io/hello-arc:latest` in it. The error is now
about missing annotation not unsupported OCI registry.
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
No.
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
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