Align desktop architecture and message turns

[novvoo]

Summary

• align architecture.md with the implemented runtime, command gateway, lifecycle ownership, maturity status, and transactional workspace switching
• introduce ConversationTurn-based message presentation so requests, tool calls, progress, and responses remain grouped under stable IDs with explicit collapse policy
• improve runtime detail cards and sidebar task cleanup, and add rollback-safe workspace switching across DesktopCore and OmpAdapter

Verification

• bun run verify
• renderer build passed
• unit tests: 469 passed
• desktop tests: 22 passed
• ESLint passed