Move regression test to test/regression/issue/26597.test.ts

Per CLAUDE.md guidelines, tests for specific GitHub issues should be
placed in test/regression/issue/${issueNumber}.test.ts for consistency
and discoverability.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/regression/issue/26597.test.ts

@@ -0,0 +1,28 @@
+// https://github.com/oven-sh/bun/issues/26597
+// Parallel file execution should work on Windows when bun path contains backslashes
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, tempDir } from "harness";
+
+test("#26597: parallel file execution works (Windows backslash path handling)", async () => {
+  using dir = tempDir("issue-26597", {
+    "a.js": "console.log('hello-a')",
+    "b.js": "console.log('hello-b')",
+  });
+
+  // This previously failed on Windows with "bun: command not found: C:Usersjake.bunbinbun.exe"
+  // because backslashes in the bun executable path were being stripped by the shell parser.
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "run", "--parallel", "a.js", "b.js"],
+    env: { ...bunEnv, NO_COLOR: "1" },
+    cwd: String(dir),
+    stderr: "pipe",
+    stdout: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  // Both scripts should run and produce prefixed output
+  expect(stdout).toMatch(/a\.js\s+\| .*hello-a/);
+  expect(stdout).toMatch(/b\.js\s+\| .*hello-b/);
+  expect(exitCode).toBe(0);
+});