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

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

packages/ui/src/lib/i18n/messages/en/folderSelection.ts

@@ -69,4 +69,5 @@ export const folderSelectionMessages = {
   "folderSelection.servers.dialog.connecting": "Connecting...",
   "folderSelection.servers.dialog.errorRequired": "Server name and URL are required.",
   "folderSelection.servers.dialog.errorConnect": "Could not connect to the remote server.",
+  "folderSelection.sidecars.button": "Open SideCar",
 } as const