feat(sidecars): add proxied sidecar tabs (#279)

## Summary
- add SideCar support across the server and UI, including proxied tabs,
picker/settings flows, and websocket-aware proxying
- unify top-level tab handling so workspace instances and SideCars share
the same tab model and navigation flows
- limit SideCars to port-based services only, removing server-managed
process control from the final API and UI

---------

Co-authored-by: Shantur <shantur@Mac.home>
Co-authored-by: Shantur <shantur@Shanturs-MacBook-Pro-M5.local>

packages/ui/src/lib/hooks/use-app-lifecycle.ts

@@ -16,6 +16,7 @@ const log = getLogger("actions")
 interface UseAppLifecycleOptions {
   setEscapeInDebounce: (value: boolean) => void
   handleNewInstanceRequest: () => void
+  handleCloseActiveTab: () => Promise<void>
   handleCloseInstance: (instanceId: string) => Promise<void>
   handleNewSession: (instanceId: string) => Promise<void>
   handleCloseSession: (instanceId: string, sessionId: string) => Promise<void>
@@ -31,7 +32,7 @@ export function useAppLifecycle(options: UseAppLifecycleOptions) {
 
     setupTabKeyboardShortcuts(
       options.handleNewInstanceRequest,
-      options.handleCloseInstance,
+      options.handleCloseActiveTab,
       options.handleNewSession,
       options.handleCloseSession,
       () => {