Expose the runtime catalog and carry an explicit runtime ID through workspace creation while preserving omitted-field compatibility for older clients.
The runtime POC made useGitActions require WorkspaceGitBoundary, but Command Center mounted that consumer without the boundary and crashed. Bind the active workspace at that consumer.
Keep provisional Worktree reservations unpublished until final placement so observers never bind the source checkout as the new workspace. Gate legacy cwd Git compatibility by hostVisiblePath instead of runtime kind because Local and Worktree remain host-visible runtimes.