fix(pi): harden image read mime

src/agents/pi-tools.test.ts

@@ -0,0 +1,32 @@
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { describe, expect, it } from "vitest";
+
+import { createClawdisCodingTools } from "./pi-tools.js";
+
+const PNG_1x1 =
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/woAAn8B9FD5fHAAAAAASUVORK5CYII=";
+
+describe("createClawdisCodingTools", () => {
+  it("sniffs mime from bytes when extension lies", async () => {
+    const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "clawdis-pi-"));
+    const filePath = path.join(tmpDir, "image.jpg"); // actually PNG bytes
+    await fs.writeFile(filePath, Buffer.from(PNG_1x1, "base64"));
+
+    const read = createClawdisCodingTools().find((t) => t.name === "read");
+    expect(read).toBeTruthy();
+    if (!read) throw new Error("read tool missing");
+
+    const res = await read.execute("toolCallId", { path: filePath });
+    const image = res.content.find(
+      (b): b is { type: "image"; mimeType: string } =>
+        !!b &&
+        typeof b === "object" &&
+        (b as Record<string, unknown>).type === "image" &&
+        typeof (b as Record<string, unknown>).mimeType === "string",
+    );
+
+    expect(image?.mimeType).toBe("image/png");
+  });
+});