docs: add AGENTS.md and CLAUDE.md for AI agent guidance

[bobbor]

Description of changes

Adds AGENTS.md and CLAUDE.md at the repo root to give AI coding agents the project conventions they need to make correct changes.

• AGENTS.md — repository/monorepo structure, environment versions, mandatory yarn-only build/test/lint commands, testing conventions (mock underlying modules, not Amplify.getConfig; bundle-size scope), code conventions (license headers, no committed tsconfig.tsbuildinfo), Husky git hooks (pre-commit + pre-push/git-secrets), changeset requirements, branch naming, commit/PR flow, the 8 CI checks, and a Do/Don't summary.
• CLAUDE.md — thin pointer to AGENTS.md so there is a single source of truth.

All content was verified against the repo (root/package package.json scripts, .github/workflows/pr.yml, .husky/, .changeset/).

Issue #, if available

N/A

Description of how you validated changes

Docs-only change. Verified every cited command/script and CI check exists in the repo before committing.

Checklist

• PR description included
• yarn test passes (N/A — docs-only, no source changes)
• Unit Tests are changed or added (N/A — docs-only)
• Relevant documentation is changed or added

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 2a8f7c2

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