feat: Make the debug bar draggable

[wpoortman]

Summary

• add a dedicated grip to move the compact debug bar by pointer or keyboard
• persist the custom position and keep it within the viewport
• keep the inspector and bubble aligned with the nearest edge
• update the committed frontend bundle, documentation, and regression coverage

Verification

• npm test — 71 passing
• npm run build
• npm run test:browser -- --list — 17 tests discovered

The browser suite could not be executed locally because its configured Chrome binary is unavailable in this environment.