[cmath10]

Summary

• Add Material 3 Search, Top app bar, and Toolbar to React and Vue with matching Storybook guides and examples.
• Introduce shared UI layers for modal surfaces, popovers, floating controls, and feedback. Popovers and snackbars follow their owning modal layer, with matching browser coverage in both workspaces.
• Stabilize browser tests that depended on font loading or Vite dependency optimization.

Breaking changes

• M3Surface.zIndex was removed. Modal stacking now follows layer activation order.
• Foundation stylesheet layer names were replaced with floating, feedback, popover, and modal; --m3-search-z-index no longer controls the search overlay.

Validation

• ESLint, package/test/E2E/Storybook type checks, package build and packed-package contracts passed.
• 367 unit tests and 97 browser E2E tests passed.
• React and Vue Storybook docs rendered without runtime errors; 240 Storybook smoke tests passed.
• Combined coverage: 85.88% (Codecov project target: 80%).
• CI workflow lint and dry-run plan, plus Node/Yarn Docker runtime parity, passed.

Closes #21
Closes #26
Closes #12