Add ESLint 10 support

[dgreif]

Summary

• install ESLint 10 by default for development and allow ESLint 9/10 as peers
• replace incompatible ecosystem dependencies with maintained aliases while preserving existing rule namespaces where possible
• update configs, tests, docs, and example projects for ESLint 10 plus ESLint 9 compatibility checks

Notes

• ESLint 8 is no longer supported because the React accessibility dependency path does not support both ESLint 8 and 10.
• Legacy React .eslintrc consumers need eslint-plugin-jsx-a11y installed directly, which is documented in the README.

Validation

• npm ci --no-audit --no-fund && npm test -- --reporter dot
• npm install --no-save --package-lock=false --no-audit --no-fund eslint@^9 && npm test -- --reporter dot
• npm run test-examples:flat
• npm run test-examples:legacy