refactor(shared): reuse isPidAlive

src/agents/session-write-lock.ts

@@ -1,6 +1,7 @@
 import fsSync from "node:fs";
 import fs from "node:fs/promises";
 import path from "node:path";
+import { isPidAlive } from "../shared/pid-alive.js";
 
 type LockFilePayload = {
   pid: number;
@@ -48,18 +49,6 @@ function resolveCleanupState(): CleanupState {
   return proc[CLEANUP_STATE_KEY];
 }
 
-function isAlive(pid: number): boolean {
-  if (!Number.isFinite(pid) || pid <= 0) {
-    return false;
-  }
-  try {
-    process.kill(pid, 0);
-    return true;
-  } catch {
-    return false;
-  }
-}
-
 /**
  * Synchronously release all held locks.
  * Used during process exit when async operations aren't reliable.
@@ -206,7 +195,7 @@ export async function acquireSessionWriteLock(params: {
       const payload = await readLockPayload(lockPath);
       const createdAt = payload?.createdAt ? Date.parse(payload.createdAt) : NaN;
       const stale = !Number.isFinite(createdAt) || Date.now() - createdAt > staleMs;
-      const alive = payload?.pid ? isAlive(payload.pid) : false;
+      const alive = payload?.pid ? isPidAlive(payload.pid) : false;
       if (stale || !alive) {
         await fs.rm(lockPath, { force: true });
         continue;