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/api-client.ts

@@ -10,6 +10,7 @@ import type {
   SpeechCapabilitiesResponse,
   SpeechSynthesisResponse,
   SpeechTranscriptionResponse,
+  SideCar,
   ServerMeta,
   RemoteServerProbeRequest,
   RemoteServerProbeResponse,
@@ -193,6 +194,33 @@ export const serverApi = {
       body: JSON.stringify(payload),
     })
   },
+  fetchSidecars(): Promise<{ sidecars: SideCar[] }> {
+    return request<{ sidecars: SideCar[] }>("/api/sidecars")
+  },
+  createSidecar(payload: {
+    kind: "port"
+    name: string
+    port: number
+    insecure: boolean
+    prefixMode: "strip" | "preserve"
+  }): Promise<SideCar> {
+    return request<SideCar>("/api/sidecars", {
+      method: "POST",
+      body: JSON.stringify(payload),
+    })
+  },
+  updateSidecar(
+    id: string,
+    payload: Partial<{ name: string; port: number; insecure: boolean; prefixMode: "strip" | "preserve" }>,
+  ): Promise<SideCar> {
+    return request<SideCar>(`/api/sidecars/${encodeURIComponent(id)}`, {
+      method: "PUT",
+      body: JSON.stringify(payload),
+    })
+  },
+  deleteSidecar(id: string): Promise<void> {
+    return request(`/api/sidecars/${encodeURIComponent(id)}`, { method: "DELETE" })
+  },
   fetchServerMeta(): Promise<ServerMeta> {
     return request<ServerMeta>("/api/meta")
   },
@@ -438,4 +466,4 @@ function buildClientEventsUrl(identity: { clientId: string; connectionId: string
   return `${url.pathname}${url.search}`
 }
 
-export type { WorkspaceDescriptor, WorkspaceLogEntry, WorkspaceEventPayload, WorkspaceEventType }
+export type { WorkspaceDescriptor, WorkspaceLogEntry, WorkspaceEventPayload, WorkspaceEventType, SideCar }