fix(app): support text attachments (#17335)

packages/app/src/components/prompt-input/attachments.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, test } from "bun:test"
+import { attachmentMime } from "./files"
+
+describe("attachmentMime", () => {
+  test("keeps PDFs when the browser reports the mime", async () => {
+    const file = new File(["%PDF-1.7"], "guide.pdf", { type: "application/pdf" })
+    expect(await attachmentMime(file)).toBe("application/pdf")
+  })
+
+  test("normalizes structured text types to text/plain", async () => {
+    const file = new File(['{"ok":true}\n'], "data.json", { type: "application/json" })
+    expect(await attachmentMime(file)).toBe("text/plain")
+  })
+
+  test("accepts text files even with a misleading browser mime", async () => {
+    const file = new File(["export const x = 1\n"], "main.ts", { type: "video/mp2t" })
+    expect(await attachmentMime(file)).toBe("text/plain")
+  })
+
+  test("rejects binary files", async () => {
+    const file = new File([Uint8Array.of(0, 255, 1, 2)], "blob.bin", { type: "application/octet-stream" })
+    expect(await attachmentMime(file)).toBeUndefined()
+  })
+})