Fix desktop voice layout and knowledge activity

[finalflash159]

Summary

• remove the dark square compositor artifact around the Voice orb and keep the immersive layout inside short/fullscreen viewports
• keep indexing and memory maintenance feedback on Knowledge instead of leaking background work into Chat
• add persistent progress, terminal failure feedback, and accessible progress semantics for Knowledge operations

Verification

• npm test --prefix desktop (267 passed)
• npm run build --prefix desktop
• npm run tauri:build --prefix desktop
• visual checks at 937×661 and 1790×768
• codesign --verify --deep --strict desktop/src-tauri/target/release/bundle/macos/SoCa.app

[qodo-code-review]

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