Add persistent workspace layout foundation and publish Beta 9

[WebCrew]

Summary

• add a versioned, validated local workspace-layout preference
• allow Hierarchy/Scenes, Inspector and Assets to be hidden and restored through View or panel close buttons
• add bounded pointer and keyboard resizing with automatic viewport resize
• add Reset Layout and restore the saved workspace on startup
• document the roadmap milestone and Beta 9 maintainer acceptance checklist
• bump the packaged preview to 0.5.0-beta.9

Scope boundary

This establishes stable docked panels only. Arbitrary drag-and-drop docking, tab groups and floating windows remain later work.

Verification

• node scripts/check.cjs
• workspace normalization rejects incompatible versions and clamps invalid sizes
• desktop boundary check verifies panel registry surfaces and preference integration
• Windows packaging and CodeQL run in GitHub Actions