Add WWDC26 Apple Intelligence support

[nimatime]

Summary

• Add Foundation Models, evaluation-suite, and preview-proof fields to the public SDK/IR/parser/generator path.
• Extend Cloud Check with Xcode 27/AppIntentsTesting readiness, evaluation, preview snapshot, Visual Intelligence, Image Playground, String Catalog, and resizable iOS layout proof diagnostics.
• Add an Xcode 27 agent plugin package and five WWDC26 proof templates.
• Sync public metrics, README, ROADMAP, and MCP template count metadata.

Verification

• npm run typecheck
• npm run lint
• npm test
• npm run metrics:check
• npm run docs:check
• node scripts/sync-roadmap-metrics.mjs --check