feat: implement websocket-stream for journal server

Integrate `websocket-stream` to handle MQTT broker upgrades in the
CLI and add granular connection status tracking to the UI.

- Add `websocket-stream` dependency
- Update CLI to use `websocket-stream` for socket upgrades
- Enhance `journalStream` store with `connectionStatus` and
  `connectionError` states
- Add visual connection status indicators to `App` and `JournalPanel`

src/components/stores/journalStream.ts

@@ -33,6 +33,10 @@ export interface JournalStreamState {
   revealedPaths: Set<string>;
   /** MQTT connection status */
   connected: boolean;
+  /** Granular connection state for UI indicators */
+  connectionStatus: "disconnected" | "connecting" | "connected" | "error";
+  /** Last connection error message, if any */
+  connectionError: string | null;
   /** This client's identity */
   myName: string;
   /** Broker URL, set after connect */
@@ -84,6 +88,8 @@ const [state, setState] = createStore<JournalStreamState>({
   senderSeq: {},
   revealedPaths: new Set(),
   connected: false,
+  connectionStatus: "disconnected",
+  connectionError: null,
   myName: persisted.myName,
   brokerUrl: persisted.brokerUrl,
 });
@@ -189,6 +195,9 @@ export async function connectStream(
 ): Promise<void> {
   const { default: mqtt } = await import("mqtt");
 
+  setState("connectionStatus", "connecting");
+  setState("connectionError", null);
+
   const client = mqtt.connect(brokerUrl, {
     clientId: `${state.myName}-${Date.now()}`,
     protocol: brokerUrl.startsWith("wss") ? "wss" : "ws",
@@ -200,6 +209,8 @@ export async function connectStream(
   client.on("connect", () => {
     _mqttConnected = true;
     setState("connected", true);
+    setState("connectionStatus", "connected");
+    setState("connectionError", null);
     setState("brokerUrl", brokerUrl);
 
     // Persist connection info for next time
@@ -251,10 +262,13 @@ export async function connectStream(
   client.on("close", () => {
     _mqttConnected = false;
     setState("connected", false);
+    setState("connectionStatus", "disconnected");
   });
 
   client.on("error", (err) => {
     console.error("[stream] mqtt error:", err);
+    setState("connectionStatus", "error");
+    setState("connectionError", err.message);
   });
 }
 
@@ -416,6 +430,7 @@ export function disconnectStream(): void {
     _mqttConnected = false;
   }
   setState("connected", false);
+  setState("connectionStatus", "disconnected");
 }
 
 // ---------------------------------------------------------------------------