fix: harden atomic file writes (#1453)

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

scripts/dev-web-hmr.mjs

@@ -146,13 +146,6 @@ async function shutdown(exitCode = 0) {
   if (shuttingDown) return;
   shuttingDown = true;
   await Promise.all([stopChildTree(api), stopChildTree(vite)]);
-  // Clean up orphaned OpenCode processes that weren't killed by
-  // the Express server's shutdown (e.g. when nodemon is killed first).
-  try {
-    spawnSync('pkill', ['-f', 'opencode serve'], { stdio: 'ignore' });
-  } catch {
-    // best-effort
-  }
   process.exit(exitCode);
 }