The selector returned a freshly constructed authority object each call, so
useSyncExternalStore saw a new reference every render and force-rerendered,
producing a maximum update depth crash. Select the specific workspace
descriptor (stable reference) and derive the authority via useMemo.
Replace hardcoded renderContent() switch and per-kind descriptor logic
with a registry-based panel interface. Each panel type (agent, draft,
terminal, file) now self-registers with its component, useDescriptor
hook, and optional confirmClose. Panels access workspace context via
usePaneContext() instead of prop drilling. This prepares the workspace
screen for split pane support.