test(gsd): add regression test for resource-loader import path

Verifies auto.ts does not use a relative import reaching above
extensions/ for resource-loader (breaks on deployment to ~/.gsd/).
Guards against regression of the fix for #3899.

src/resources/extensions/gsd/tests/resource-loader-import-path.test.ts

@@ -0,0 +1,37 @@
+// GSD2 — Regression test for broken resource-loader import path
+// Ensures auto.ts imports resource-loader via package resolution, not a
+// relative path that breaks when deployed to ~/.gsd/agent/extensions/gsd/.
+
+import { describe, test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+const autoSrc = readFileSync(join(import.meta.dirname, "..", "auto.ts"), "utf-8");
+
+describe("resource-loader import path", () => {
+  test("must not use relative import reaching above extensions/", () => {
+    // The old broken pattern: import("../../../" + "resource-loader.js")
+    // This resolves to ~/.gsd/resource-loader.js from deployed location, which
+    // doesn't exist. Regression introduced in #3899.
+    const brokenPattern = /import\(\s*["']\.\.\/\.\.\/\.\..*resource-loader/;
+    assert.ok(
+      !brokenPattern.test(autoSrc),
+      "auto.ts must not import resource-loader via relative path above extensions/ — " +
+      "breaks when deployed to ~/.gsd/agent/extensions/gsd/ (see #3899)",
+    );
+  });
+
+  test("uses createRequire to resolve resource-loader from package root", () => {
+    // The fix uses createRequire to find gsd-pi/package.json, then imports
+    // dist/resource-loader.js from there — works in both source and deployed.
+    assert.ok(
+      autoSrc.includes('createRequire(import.meta.url)'),
+      "auto.ts should use createRequire to resolve resource-loader",
+    );
+    assert.ok(
+      autoSrc.includes('resolve("gsd-pi/package.json")'),
+      "auto.ts should resolve gsd-pi package root via package.json",
+    );
+  });
+});