feat: introduces the new home for the ai controllers

[zone-live]

Explanation

This PR adds a new package @metamask/ai-controllers to serve as the home for AI related controllers.
Subsequent PRs will add the actual controllers implementations.

• Added team-social-ai as the owner in teams.json
• Updated .github/CODEOWNERS

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
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Establishes a new package for AI controllers and wires it into the monorepo.

• Adds @metamask/ai-controllers with scaffolded code (src/index.ts greeter), tests, build/docs configs (package.json, jest.config.js, tsconfig*, typedoc.json), README.md, LICENSE, and CHANGELOG.md
• Updates monorepo metadata: includes package in README.md (list and graph), tsconfig.json and tsconfig.build.json references, yarn.lock workspace entry
• Sets ownership and release mappings: CODEOWNERS (Social AI team) and teams.json, plus package release file ownership entries

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