test: add regression test for worktree expected-condition warning suppression

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/resources/extensions/gsd/tests/worktree-expected-warnings.test.ts

@@ -0,0 +1,38 @@
+/**
+ * worktree-expected-warnings.test.ts — #3665
+ *
+ * Verify that auto-worktree.ts and worktree-manager.ts suppress expected
+ * ENOENT and EISDIR conditions instead of logging misleading warnings.
+ */
+
+import { describe, test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const autoWorktreeFile = join(__dirname, "..", "auto-worktree.ts");
+const worktreeManagerFile = join(__dirname, "..", "worktree-manager.ts");
+
+describe("worktree expected-condition warning suppression (#3665)", () => {
+  const autoSource = readFileSync(autoWorktreeFile, "utf-8");
+
+  test("auto-worktree.ts checks for ENOENT before logging unlink warning", () => {
+    assert.match(autoSource, /code\s*!==\s*["']ENOENT["']/);
+  });
+
+  test("auto-worktree.ts checks for EISDIR before logging unlink warning", () => {
+    assert.match(autoSource, /code\s*!==\s*["']EISDIR["']/);
+  });
+
+  test("auto-worktree.ts references issue #3597", () => {
+    assert.match(autoSource, /#3597/);
+  });
+
+  const managerSource = readFileSync(worktreeManagerFile, "utf-8");
+
+  test("worktree-manager.ts checks isDirectory() before reading .git file", () => {
+    assert.match(managerSource, /lstatSync\(gitPath\)\.isDirectory\(\)/);
+  });
+});