feat: implement temporary code freeze with core-platform as sole CODEOWNERS

[cryptodev-2s]

Explanation

During the messenger migration period, all changes require approval from the core-platform team. This is a temporary measure to maintain control during critical migrations.

Changes:

• Added code freeze notice to CODEOWNERS
• Set @MetaMask/core-platform as owner of all files (*)
• Commented out all existing ownership rules for preservation
• Original rules can be easily restored after migrations are complete

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

---

Note

Temporarily assigns @MetaMask/core-platform as owner of all files and disables Yarn codeowner validation during migration.

• CODEOWNERS:
  • Add temporary code-freeze notice and set global * @MetaMask/core-platform.
  • Comment out all previous per-package ownership rules for later restoration.
• Tooling (Yarn constraints):
  • Disable codeowner validation by commenting out expectCodeowner invocation and implementation in yarn.config.cjs.

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