[DevMando]

Summary

Desktop now groups agents into named workspaces, so users can keep separate streams of work organized without mixing every agent into one tab row. For example, a Website workspace can keep a two-agent split while a Backend workspace shows a different conversation. Switching between them preserves each arrangement and lets background agents keep working.

This PR also includes the pending file-picker and agent-collaboration improvements on this branch.

What changed

• Two levels of tabs: workspaces occupy the upper row; agents, Split, and New agent sit below and apply to the selected workspace. Both rows reserve matching space beneath the tabs for horizontal scrollbars.
• Workspace controls: create, rename, switch, and close workspaces. A small × appears on the selected tab and when another tab is hovered or focused, without shifting its label. Right-click Rename and Close remain available. Keyboard shortcuts support creation, switching, and closing.
• Continuity and attention: each workspace saves its selected agent and split layout. Existing tabs migrate into Main, preserving their conversation identities and model selections. Workspace badges show background work and pending approvals; approval notices can take the user to an agent in another workspace.
• Closing safeguards: users must keep one workspace open. A workspace cannot close while its agents or commands are running or approvals are waiting. Conversations are saved to History before its agents close; an archive-save failure keeps the workspace open.
• Clearer, faster mentions: typing @ opens Files first; Tab switches between Files and Agents. Agent results include the workspace and project folder. File lookup uses background indexing and loading feedback, handles paths with spaces, and preserves selection as results update.
• More agent collaboration: agents can ask for immediate or background answers, send messages, request read-only reviews, hand off work, and update or cancel individual jobs. Attributed, expandable transcript entries show messages and results. Closing an agent cancels its associated jobs.
• Engine and documentation: pin the published MandoCode CLI v0.16.1 engine (277cd36), update the README and agent-mentions guide, and document the changes under Unreleased.

Why this was done

A flat agent list becomes harder to navigate as several projects or tasks run at once. Workspaces add a visible grouping above agents while preserving the Desktop conversation experience. Keeping Split and New agent on the lower row makes their scope clear.

How it was tested

• Release application build passed with zero warnings and errors.
• All 604 Desktop tests passed in Release, including workspace-state migration, save/load round trips, duplicate workspace-ID rejection, mention/file lookup, and agent interactions.
• Manual checks covered migration of the existing conversation and model into Main, creating a workspace, adding agents, entering split view, switching to Main and back without losing the split, and opening the Rename workspace dialog.
• Remaining interactive checks before merge: full application-restart restoration, streaming and approval handling in hidden workspaces, and the final × hover/focus behavior and workspace-close safeguards. The final close-button UI was compiled successfully.

Notes

• This is a feature PR; the application version is unchanged.
• The engine's local launchSettings.json edit is excluded.