Use STORYKIT_PORT for both backend and frontend, add .story_kit_port to ignore files

Single env var STORYKIT_PORT configures backend port, frontend proxy target,
frontend dev server port (port + 2172), and WebSocket host. Added .story_kit_port
to .gitignore and .ignore to prevent git tracking and cargo watch restart loops.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/api/client.ts

@@ -54,6 +54,8 @@ export interface CommandOutput {
 	exit_code: number;
 }
 
+declare const __STORYKIT_PORT__: string;
+
 const DEFAULT_API_BASE = "/api";
 const DEFAULT_WS_PATH = "/ws";
 
@@ -235,7 +237,7 @@ export class ChatWebSocket {
 		const protocol = window.location.protocol === "https:" ? "wss" : "ws";
 		const wsHost = resolveWsHost(
 			import.meta.env.DEV,
-			import.meta.env.VITE_STORYKIT_PORT,
+			typeof __STORYKIT_PORT__ !== "undefined" ? __STORYKIT_PORT__ : undefined,
 			window.location.host,
 		);
 		const wsUrl = `${protocol}://${wsHost}${wsPath}`;

frontend/vite.config.ts

@@ -3,14 +3,17 @@ import { defineConfig } from "vite";
 
 // https://vite.dev/config/
 export default defineConfig(() => {
-  const backendPort = process.env.VITE_STORYKIT_PORT || "3001";
+  const backendPort = Number(process.env.STORYKIT_PORT || "3001");
   return {
     plugins: [react()],
+    define: {
+      __STORYKIT_PORT__: JSON.stringify(String(backendPort)),
+    },
     server: {
-      port: 5173,
+      port: backendPort + 2172,
       proxy: {
         "/api": {
-          target: `http://127.0.0.1:${backendPort}`,
+          target: `http://127.0.0.1:${String(backendPort)}`,
           timeout: 120000,
         },
       },