feat(plugin): refine Relight Studio Radix UI

[superche]

Summary

• refresh Relight Studio with a white and Radix Violet/Mauve visual system
• improve the Canvas preview hierarchy, empty-state guidance, preset cards, controls, and narrow-window layout
• extend the local Radix bundle from Select and Slider to include value Tooltips
• bump Relight Studio to 0.1.2 and Registry sequence to 26

Impact

The plugin is easier to scan and operate while preserving its existing WebGL preview, scoped host communication, and Canvas generation behavior. The install ZIP remains inert and self-contained.

Validation

• bun install --frozen-lockfile --ignore-scripts
• package workspace builds and companion builds
• bun run validate — 16 packages
• bun run workspaces:typecheck — 3 workspaces
• bun run workspaces:test — 150 tests
• bun test — 207 tests
• bun run pack
• bun run build:index
• Playwright visual and accessibility checks at 1080×720 and 720×720, including Radix Tooltip behavior