Add AddBunApp for Bun-native apps

playground/AspireWithBun/BunFrontend/package.json

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+{
+  "name": "bunfrontend",
+  "version": "1.0.0",
+  "type": "module",
+  "private": true,
+  "scripts": {
+    "start": "bun server.ts"
+  },
+  "dependencies": {
+    "ms": "^2.1.3"
+  },
+  "devDependencies": {
+    "chalk": "^5.6.2"
+  }
+}

playground/AspireWithBun/BunFrontend/server.ts

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+// Minimal Bun HTTP server used by the AspireWithBun playground and BunFunctionalTests.
+// Distinguishes between direct invocation (`bun server.ts`) and package-script invocation
+// (`bun run start`) by checking `npm_lifecycle_event`, which Bun sets when running a script.
+
+const port = Number(process.env.PORT ?? 3000);
+const isScriptRun = process.env.npm_lifecycle_event !== undefined;
+const greeting = isScriptRun ? "Hello from bun script!" : "Hello from bun!";
+
+const server = Bun.serve({
+    port,
+    fetch(_req) {
+        return new Response(greeting, {
+            headers: { "Content-Type": "text/plain" },
+        });
+    },
+});
+
+console.log(`Bun server listening on http://${server.hostname}:${server.port}`);

playground/AspireWithBun/README.md

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+# AspireWithBun
+
+A minimal Aspire **TypeScript AppHost** that hosts a [Bun](https://bun.com/) HTTP server two different ways:
+
+| Resource    | API                                                        | Behavior                                          |
+|-------------|------------------------------------------------------------|---------------------------------------------------|
+| `bunapp`    | `addBunApp("bunapp", "./BunFrontend", "server.ts")`        | Runs `bun server.ts` directly.                    |
+| `bunscript` | `addBunApp(...).withRunScript("start")`                    | Runs `bun run start` against the `start` script.  |
+
+Both resources serve a simple `text/plain` greeting and use `Bun.serve`.
+
+## Prerequisites
+
+- [Aspire CLI](https://learn.microsoft.com/dotnet/aspire/) on PATH
+- [Bun](https://bun.com/docs/installation) on PATH
+- Node.js (used to host the TypeScript AppHost itself)
+
+## Run
+
+```bash
+aspire run
+```
+
+The CLI generates the `.aspire/modules/` TypeScript bindings the first time it runs, then starts the AppHost. Open the URL listed for `bunapp` or `bunscript` in the dashboard. Each returns a different greeting so you can confirm which entry path served the response.

playground/AspireWithBun/apphost.mts

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+// Aspire TypeScript AppHost — exercises the Aspire.Hosting.JavaScript `AddBunApp` API.
+// Run with: aspire run
+// Publish with: aspire publish (emits Docker Compose + Dockerfiles using oven/bun:1)
+
+import { createBuilder } from './.aspire/modules/aspire.mjs';
+
+const builder = await createBuilder();
+
+await builder.addDockerComposeEnvironment("compose");
+
+// Direct file execution: `bun server.ts`
+await builder
+    .addBunApp("bunapp", "./BunFrontend", "server.ts")
+    .withHttpEndpoint({ env: "PORT" })
+    .withExternalHttpEndpoints();
+
+// Package-script execution: `bun run start` (uses the `start` script in package.json)
+await builder
+    .addBunApp("bunscript", "./BunFrontend", "server.ts")
+    .withRunScript("start")
+    .withHttpEndpoint({ env: "PORT" })
+    .withExternalHttpEndpoints();
+
+await builder.build().run();

playground/AspireWithBun/aspire.config.json

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+{
+  "appHost": {
+    "path": "apphost.mts",
+    "language": "typescript/nodejs"
+  },
+  "packages": {
+    "Aspire.Hosting.JavaScript": "",
+    "Aspire.Hosting.Docker": ""
+  }
+}