fix(@angular/cli): promote zoneless migration MCP tool to stable

[clydin]

The zoneless migration tool has been moved from the experimental to the stable toolset within the MCP server, making it available by default.

[clydin]

This PR was merged into the repository. The changes were merged into the following branches:

• main: ea4fb9d
• 21.0.x: 1be35b3

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}