fix: contain google demo runtime rail

[creatornader]

Summary

• make the Google demo runtime progress rail a bounded responsive grid
• add a visual regression assertion that the rail does not overflow before or after an active runtime run

Checks

• pnpm --filter @atrib/integration test -- google-stack-chain-visual
• pnpm --filter @atrib/integration typecheck
• pnpm exec prettier --check packages/integration/examples/google-stack-chain/visual/styles.css packages/integration/test/google-stack-chain-visual.test.ts
• git diff --check