refactor(runtime): compose consumers over fs and subprocess

packages/subprocess/subprocess-local/scripts/ensure-spawn-helper.mjs

@@ -0,0 +1,16 @@
+/** Restore the executable bit stripped from node-pty's prebuilt helper. */
+
+import { chmodSync, existsSync } from 'node:fs'
+import { dirname, join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const entry = fileURLToPath(import.meta.resolve('node-pty'))
+const packageRoot = dirname(dirname(entry))
+const candidates = [
+  join(packageRoot, 'prebuilds', `${process.platform}-${process.arch}`, 'spawn-helper'),
+  join(packageRoot, 'build', 'Release', 'spawn-helper'),
+]
+
+for (const helper of candidates) {
+  if (existsSync(helper)) chmodSync(helper, 0o755)
+}