2.0.5-beta: Nest, calls, settings, screen share

[krwg]

Summary

• Nest sound pack + NestUI 1.2 (liquid glass, richer shadows, glass/radius customization)
• Settings: Call/Shortcuts nav fix, less empty stretch, readable error catalog, window-style toast
• Calls: strict 2×2 MUTE/DEAFEN/MORE/END; camera in MORE; video fallback instead of hard fail (305)
• Screen share: better Windows window enumeration (0×0 thumbs); stop tears down screen audio + restores UI

Test plan

• Settings → Call / Shortcuts open and scroll; no huge empty glass under short panels
• Developer → error catalog readable; window style mac/win applies + toast
• Sound → Nest pack; Appearance → NestUI 1.2 + glass/radius sliders
• Call: 2×2 grid; MORE has screen/camera/volume; camera on/off mid-call
• Video call Win↔Mac; denied camera falls back to voice with toast (not silent 999)
• Screen picker lists more windows; stop share ends system audio and layout recovers

Notes

Do not ship another release tag until this PR CI is green and merged (same flow as #142).