fix: improve Windows CLI compatibility

[adrenjc]

Summary

• replace the POSIX shell wrapper with a Node-based wrapper so npm shims on Windows no longer require /bin/sh
• fix the Windows .cmd wrapper to invoke the correct entry script
• avoid DETACHED_PROCESS in headed mode on Windows so the browser window appears

Test plan

• npm test

[vercel]

@adrenjc is attempting to deploy a commit to the Vercel Labs Team on Vercel.

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[vercel]

Suggested change

	const [{ accessSync, constants, existsSync, realpathSync }, { spawn }, { dirname, join }] =
	await Promise.all([import('fs'), import('child_process'), import('path')]);
	const scriptArg = process.argv[1];
	if (!scriptArg) {
	console.error('Error: Missing script path for agent-browser wrapper');
	process.exit(1);
	}
	let scriptPath;
	try {
	scriptPath = realpathSync(scriptArg);
	} catch (err) {
	const message = err instanceof Error ? err.message : String(err);
	console.error(`Error: Failed to resolve script path: ${message}`);
	process.exit(1);
	}
	const [{ accessSync, constants, existsSync, realpathSync }, { spawn }, { dirname, join }, { fileURLToPath }] =
	await Promise.all([import('fs'), import('child_process'), import('path'), import('url')]);
	const scriptPath = realpathSync(fileURLToPath(import.meta.url));

process.argv[1] is unreliable for determining script path when invoked through npm shims, should use import.meta.url instead