[ai] add Claude config

[pq]

See: #8895

Adds Claude.md config.

The @.gemini/styleguide.md import pulls in the full styleguide automatically, and the additional rules below it mirror the key generation rules for Gemini from .aiconfig.

---

Review the contribution guidelines below:

• I’ve reviewed the contributor guide and applied the relevant portions to this PR.
• I've included the required information in the description above.
• My up-to-date information is in the AUTHORS file.
• I've updated CHANGELOG.md if appropriate.

Contribution guidelines:

• See
  our contributor guide and
  the Flutter organization contributor guide
  for general expectations for PRs.
• Larger or significant changes should be discussed in an issue before creating a PR.
• Dart contributions to our repos should follow the Dart style guide and use
  dart format.
• Java and Kotlin contributions should strive to follow Java and Kotlin best
  practices (discussion).

[gemini-code-assist]

Code Review

This pull request introduces CLAUDE.md, a new guide for Claude Code that outlines architectural rules and coding standards for the Flutter IntelliJ Plugin. A review comment correctly identifies that the new file is missing the mandatory Chromium Authors copyright header, providing a suggestion to resolve this in accordance with the repository's style guide.

[cj-radcliff]

Do claude or other agents know the details of these things? Chromium standard copyright? what is a nit?