fix(cli): account for text strokes in contrast checks

[miguel-heygen]

Summary

• recognize solid -webkit-text-stroke paint during browser contrast audits
• hide and restore stroke paint while sampling the true background
• use the stronger fill-or-stroke contrast result for outlined captions
• keep the HyperFrames creative contrast-report helper in sync
• add browser regression coverage for white text with an 8px black outline

Verification

• bun run --cwd packages/cli test --run src/commands/layout-audit.browser.test.ts (39 tests passed)
• bunx oxfmt --check packages/cli/src/commands/contrast-audit.browser.js packages/cli/src/commands/layout-audit.browser.test.ts skills/hyperframes-creative/scripts/contrast-report.mjs
• node --check skills/hyperframes-creative/scripts/contrast-report.mjs
• git diff --check

The package typecheck was attempted, but a fresh worktree lacks generated packages/core/src/generated/runtime-inline modules; CI generates these before the full typecheck.