feat(electrobun): multi-machine relay + OTEL telemetry

Multi-machine relay:
- relay-client.ts: WebSocket client for agor-relay with token auth,
  exponential backoff (1s-30s), TCP probe, heartbeat (15s ping)
- machines-store.svelte.ts: remote machine state tracking
- RemoteMachinesSettings.svelte: machine list, add/connect/disconnect UI
- 7 RPC types (remote.connect/disconnect/list/send/status + events)

Telemetry:
- telemetry.ts: OTEL spans + OTLP/HTTP export to Tempo,
  controlled by AGOR_OTLP_ENDPOINT env var
- telemetry-bridge.ts: tel.info/warn/error frontend convenience API
- telemetry.log RPC for frontend→Bun tracing

ui-electrobun/src/bun/index.ts

@@ -10,9 +10,15 @@ import { SidecarManager } from "./sidecar-manager.ts";
 import type { PtyRPCSchema } from "../shared/pty-rpc-schema.ts";
 import { randomUUID } from "crypto";
 import { SearchDb } from "./search-db.ts";
+import { checkForUpdates, getLastCheckTimestamp } from "./updater.ts";
+import { RelayClient } from "./relay-client.ts";
+import { initTelemetry, telemetry } from "./telemetry.ts";
 import { homedir } from "os";
 import { join } from "path";
 
+/** Current app version — sourced from electrobun.config.ts at build time. */
+const APP_VERSION = "0.0.1";
+
 const DEV_SERVER_PORT = 9760; // Project convention: 9700+ range
 const DEV_SERVER_URL = `http://localhost:${DEV_SERVER_PORT}`;
 
@@ -21,8 +27,12 @@ const DEV_SERVER_URL = `http://localhost:${DEV_SERVER_PORT}`;
 const ptyClient = new PtyClient();
 const sidecarManager = new SidecarManager();
 const searchDb = new SearchDb();
+const relayClient = new RelayClient();
 const PLUGINS_DIR = join(homedir(), ".config", "agor", "plugins");
 
+// Initialize telemetry (console-only unless AGOR_OTLP_ENDPOINT is set)
+initTelemetry();
+
 async function connectToDaemon(retries = 5, delayMs = 500): Promise<boolean> {
   for (let attempt = 1; attempt <= retries; attempt++) {
     try {
@@ -874,6 +884,103 @@ const rpc = BrowserView.defineRPC<PtyRPCSchema>({
           return { ok: false, content: "", error };
         }
       },
+
+      // ── Updater handlers ──────────────────────────────────────────────────
+
+      "updater.check": async () => {
+        try {
+          const result = await checkForUpdates(APP_VERSION);
+          return { ...result, error: undefined };
+        } catch (err) {
+          const error = err instanceof Error ? err.message : String(err);
+          console.error("[updater.check]", err);
+          return {
+            available: false,
+            version: "",
+            downloadUrl: "",
+            releaseNotes: "",
+            checkedAt: Date.now(),
+            error,
+          };
+        }
+      },
+
+      "updater.getVersion": () => {
+        return {
+          version: APP_VERSION,
+          lastCheck: getLastCheckTimestamp(),
+        };
+      },
+
+      // ── Remote machine (relay) handlers ──────────────────────────────────
+
+      "remote.connect": async ({ url, token, label }) => {
+        try {
+          const machineId = await relayClient.connect(url, token, label);
+          return { ok: true, machineId };
+        } catch (err) {
+          const error = err instanceof Error ? err.message : String(err);
+          console.error("[remote.connect]", err);
+          return { ok: false, error };
+        }
+      },
+
+      "remote.disconnect": ({ machineId }) => {
+        try {
+          relayClient.disconnect(machineId);
+          return { ok: true };
+        } catch (err) {
+          const error = err instanceof Error ? err.message : String(err);
+          console.error("[remote.disconnect]", err);
+          return { ok: false, error };
+        }
+      },
+
+      "remote.list": () => {
+        try {
+          return { machines: relayClient.listMachines() };
+        } catch (err) {
+          console.error("[remote.list]", err);
+          return { machines: [] };
+        }
+      },
+
+      "remote.send": ({ machineId, command, payload }) => {
+        try {
+          relayClient.sendCommand(machineId, command, payload);
+          return { ok: true };
+        } catch (err) {
+          const error = err instanceof Error ? err.message : String(err);
+          console.error("[remote.send]", err);
+          return { ok: false, error };
+        }
+      },
+
+      "remote.status": ({ machineId }) => {
+        try {
+          const info = relayClient.getStatus(machineId);
+          if (!info) {
+            return { status: "disconnected" as const, latencyMs: null, error: "Machine not found" };
+          }
+          return { status: info.status, latencyMs: info.latencyMs };
+        } catch (err) {
+          const error = err instanceof Error ? err.message : String(err);
+          console.error("[remote.status]", err);
+          return { status: "error" as const, latencyMs: null, error };
+        }
+      },
+
+      // ── Telemetry handler ────────────────────────────────────────────────
+
+      "telemetry.log": ({ level, message, attributes }) => {
+        try {
+          telemetry.log(level, `[frontend] ${message}`, attributes ?? {});
+          return { ok: true };
+        } catch (err) {
+          console.error("[telemetry.log]", err);
+          return { ok: false };
+        }
+      },
     },
 
     messages: {},
@@ -900,6 +1007,29 @@ ptyClient.on("session_closed", (msg) => {
   }
 });
 
+// ── Forward relay events to WebView ─────────────────────────────────────────
+
+relayClient.onEvent((machineId, event) => {
+  try {
+    rpc.send["remote.event"]({
+      machineId,
+      eventType: event.type,
+      sessionId: event.sessionId,
+      payload: event.payload,
+    });
+  } catch (err) {
+    console.error("[remote.event] forward error:", err);
+  }
+});
+
+relayClient.onStatus((machineId, status, error) => {
+  try {
+    rpc.send["remote.statusChange"]({ machineId, status, error });
+  } catch (err) {
+    console.error("[remote.statusChange] forward error:", err);
+  }
+});
+
 // ── App window ───────────────────────────────────────────────────────────────
 
 async function getMainViewUrl(): Promise<string> {