feat(kumo): add ColorPicker with docs and registry integration

[singkia]

Summary

• add a ColorPicker component with hex-in hex-out behavior, popover panel, HSB area, hue slider, format switching, and progressive EyeDropper support
• add the Color Picker docs page and demo set, and wire it into docs navigation and search
• update registry metadata and generated artifacts so the API reference exposes the current public props, including onChange
• tighten the trigger layout and add regression coverage for controlled value syncing, normalized hex commits, and swatch-only rendering

Testing

• pnpm tsx ci/scripts/validate-kumo-changeset.ts
• pnpm --filter @cloudflare/kumo exec vitest run --project=unit src/components/color-picker/color-picker.test.tsx
• pnpm --filter @cloudflare/kumo exec vitest run scripts/component-registry/index.test.ts
• pnpm --filter @cloudflare/kumo codegen:registry

[singkia]

Manual verification on the docs page:

• /components/color-picker loads and the hero demo renders correctly
• search returns Color Picker with the dedicated summary
• PropsTable component="ColorPicker" renders and now includes onChange
• the swatch-only and disabled examples behave as expected

I did not attach screenshots here because the change is straightforward to review in the docs preview and the PR body already covers the scope.

[singkia]

Color Picker is now fully wired into the docs surface:

• Sidebar: Color Picker is now listed in the component nav.
• Search: ColorPicker now appears as a dedicated search result.
• Docs page: /components/color-picker now exists with demos and API reference.

Area	Before	After
Sidebar
Search
Docs page

Close-up from the docs page: