fix(ql3): stream sparse process logs within exact byte quotas

packages/ql3-local-process/test/helpers/quotaEnvironment.cjs

@@ -0,0 +1,22 @@
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const { spawnSync } = require('node:child_process');
+
+// macOS has no production /proc identity. Tests with a fake identity provider
+// still use real GNU utilities, so BSD semantics cannot mask Linux regressions.
+function quotaEnvironment(directory) {
+  if (process.platform !== 'darwin') return {};
+  const bin = path.join(directory, 'quota-bin');
+  fs.mkdirSync(bin, { mode: 0o700 });
+  for (const [name, installed] of [['head', 'ghead'], ['stdbuf', 'stdbuf']]) {
+    const found = spawnSync('/bin/sh', ['-c', `command -v ${installed}`], {
+      encoding: 'utf8',
+    });
+    assert.equal(found.status, 0, `macOS launcher tests require coreutils ${installed}`);
+    fs.symlinkSync(found.stdout.trim(), path.join(bin, name));
+  }
+  return { PATH: `${bin}:/usr/bin:/bin` };
+}
+
+module.exports = { quotaEnvironment };