Add optional plugin market and Query navigation

[wisdomqin]

What changed

• add an optional, allowlisted dsh-market installer and uninstaller for the Desktop web profile
• expose Plugin Market settings and preserve plugins installed through the market when dsh-market itself is removed
• add a compact Query navigation rail with active-query tracking, previews, independent scrolling, and hidden scrollbar
• remove archived sessions from the refreshed mobile session list
• make the phone-pairing window follow the active light or dark appearance
• reconcile the new Electron-native directory picker with the Host API proxy so Harness can boot without the legacy picker service

Why

These changes make community plugin discovery opt-in and safe, improve navigation in long sessions, and fix session and theme consistency across Desktop and the phone remote. The directory-picker adjustment resolves a runtime integration conflict introduced when main moved Windows folder selection to Electron IPC.

Validation

• npm test — 79 tests passed
• npm run typecheck
• npm run build
• local packaged Harness endpoint loaded successfully with HTTP 200