Remove hardcoded Tailscale IP, bind server and Vite to localhost only

The Express server was binding to both 127.0.0.1 and a specific Tailscale IP
(100.84.4.113), creating two separate http.Server instances. Simplify to a
single localhost binding. Also update Vite dev server to use 127.0.0.1 instead
of the Tailscale IP and disable the HMR error overlay which obscures the UI
during development.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/server/index.ts

@@ -28,18 +28,12 @@ export function createApp() {
   return app;
 }
 
-const TAILSCALE_IP = "100.84.4.113";
-
 export function startServer() {
   const PORT = parseInt(process.env.PORT || "3848", 10);
   const app = createApp();
 
-  // Bind to both localhost and Tailscale — not the public interface
-  const localServer = app.listen(PORT, "127.0.0.1", () => {
+  const server = app.listen(PORT, "127.0.0.1", async () => {
     console.log(`Session Viewer API running on http://localhost:${PORT}`);
-  });
-  const tsServer = app.listen(PORT, TAILSCALE_IP, async () => {
-    console.log(`Session Viewer API running on http://${TAILSCALE_IP}:${PORT}`);
     if (process.env.SESSION_VIEWER_OPEN_BROWSER === "1") {
       const { default: open } = await import("open");
       open(`http://localhost:${PORT}`);
@@ -48,13 +42,12 @@ export function startServer() {
 
   // Graceful shutdown so tsx watch can restart cleanly
   function shutdown() {
-    localServer.close();
-    tsServer.close();
+    server.close();
   }
   process.on("SIGINT", shutdown);
   process.on("SIGTERM", shutdown);
 
-  return tsServer;
+  return server;
 }
 
 // Only auto-start when run directly (not imported by tests)

vite.config.ts

@@ -12,10 +12,10 @@ export default defineConfig({
   },
   server: {
     port: 3847,
-    // Vite only supports one host. Use Tailscale IP so it's reachable
-    // from both the local machine (via the TS IP) and the tailnet.
-    // localhost:3847 won't work for the Vite dev server — use the TS IP.
-    host: "100.84.4.113",
+    host: "127.0.0.1",
+    hmr: {
+      overlay: false,
+    },
     proxy: {
       "/api": {
         target: "http://127.0.0.1:3848",