Fix the release build: skip windows metadata when cross-compiling

`bun build --compile --target=bun-windows-x64` rejects `--windows-title` unless
the host is Windows:

    error: Using --windows-title is only available when compiling on Windows
    build failed for windows-x64 (exit 1)

CI releases all five targets from one Ubuntu runner, so the flag failed the
release on the last of the five builds — after the other four had already been
produced. Locally on Windows it passed, which is why it shipped.

The metadata is now stamped only on a Windows host. The published binary goes
without it rather than the release failing.

Extracted `buildArgs()` so the host-dependent branch is testable: the previous
version could only be checked by running a five-platform build on two operating
systems.

scripts/release.ts

@@ -20,6 +20,26 @@ export const TARGETS: Target[] = [
 
 const OUT = 'dist/release';
 
+/**
+ * Build arguments for one target.
+ *
+ * Executable metadata can only be stamped by a Windows host: bun rejects
+ * `--windows-title` when cross-compiling, and CI releases every target from one
+ * Ubuntu runner. The published binary goes without it rather than the release
+ * failing on the last of five builds.
+ */
+export function buildArgs(t: Target, outfile: string, host = process.platform): string[] {
+  const args = ['build', '--compile', '--minify', `--target=${t.target}`, 'src/cli.tsx', '--outfile', outfile];
+  if (t.windows && host === 'win32') {
+    args.push(
+      '--windows-title=shiro-neko',
+      '--windows-description=Agentic coding CLI',
+      `--windows-version=${VERSION.split('-')[0]}.0`,
+    );
+  }
+  return args;
+}
+
 /**
  * Builds one executable per platform.
  *
@@ -58,16 +78,7 @@ async function main(): Promise<void> {
     const base = `shiro-${t.name}`;
     const outfile = join(OUT, base);
 
-    const buildArgs = ['build', '--compile', '--minify', `--target=${t.target}`, 'src/cli.tsx', '--outfile', outfile];
-    if (t.windows) {
-      buildArgs.push(
-        '--windows-title=shiro-neko',
-        '--windows-description=Agentic coding CLI',
-        `--windows-version=${VERSION.split('-')[0]}.0`,
-      );
-    }
-
-    const proc = Bun.spawn(['bun', ...buildArgs], { stdout: 'inherit', stderr: 'inherit' });
+    const proc = Bun.spawn(['bun', ...buildArgs(t, outfile)], { stdout: 'inherit', stderr: 'inherit' });
     const code = await proc.exited;
     if (code !== 0) {
       console.error(`\nbuild failed for ${t.name} (exit ${code})`);

test/version.test.ts

@@ -34,3 +34,24 @@ test('every release target is a real bun target triple', async () => {
   const { TARGETS } = await import('../scripts/release');
   for (const t of TARGETS) expect(t.target).toMatch(/^bun-(linux|darwin|windows)-(x64|arm64)$/);
 });
+
+test('windows metadata is stamped on a windows host and skipped elsewhere', async () => {
+  const { TARGETS, buildArgs } = await import('../scripts/release');
+  const win = TARGETS.find((t) => t.windows)!;
+
+  expect(buildArgs(win, 'out.exe', 'win32')).toContain('--windows-title=shiro-neko');
+  // bun rejects --windows-title when cross-compiling, and CI releases from Ubuntu.
+  // Passing it there failed the whole release on the last of five builds.
+  expect(buildArgs(win, 'out.exe', 'linux').join(' ')).not.toContain('--windows-');
+});
+
+test('every target compiles the same entrypoint with the same flags', async () => {
+  const { TARGETS, buildArgs } = await import('../scripts/release');
+  for (const t of TARGETS) {
+    const args = buildArgs(t, `out-${t.name}`, 'linux');
+    expect(args).toContain('--compile');
+    expect(args).toContain('--minify');
+    expect(args).toContain(`--target=${t.target}`);
+    expect(args).toContain('src/cli.tsx');
+  }
+});