[EhabY]

Implements VSC-1: the experimental Coder Workspaces view, built on @repo/ui.

• Lists workspaces with All, Mine, and Shared filters, nested agents and dev containers, each app's latest status, live agent metadata, and an Agent badge for workspaces with Agent chats.
• Opens a workspace or agent in VS Code or the dashboard. Settings works; the other overflow-menu actions are disabled placeholders.
• Shows sign-in, loading, empty, and error states. If a refresh fails, the view keeps the last list behind a warning banner with Retry. The filter bar shows how long ago the list was updated.
• Watches an agent's metadata only while its Metadata row is expanded.
• Looks up Agent chats in batches of 25, and stops on deployments that don't support them until the next manual refresh.

Also adds Banner to @repo/ui, makes DropdownMenu non-modal by default, and compiles package sources with the React Compiler in webview tests. A render-cost test checks that clock ticks don't rebuild the tree.

[linear-code]

VSC-1