fix: finish lingering subagent wrapper runs

src/wrapper/cli.mjs

@@ -3,6 +3,13 @@ import { spawn } from "node:child_process";
 import { normalizePiEvent } from "./normalize.mjs";
 import { renderHeader, renderEventLine } from "./render.mjs";
 
+const SEMANTIC_EXIT_GRACE_MS = 250;
+const FORCED_EXIT_GRACE_MS = 250;
+
+async function sleep(ms) {
+  await new Promise((resolve) => setTimeout(resolve, ms));
+}
+
 async function appendJsonLine(path, value) {
   await appendBestEffort(path, `${JSON.stringify(value)}\n`);
 }
@@ -68,8 +75,26 @@ async function runWrapper(meta, startedAt) {
   let stdoutBuffer = "";
   let stderrText = "";
   let spawnError;
+  let childClosed = false;
+  let completionCleanupStarted = false;
+  let child;
   let queue = Promise.resolve();
 
+  const forceChildExitAfterSemanticCompletion = async () => {
+    if (completionCleanupStarted) return;
+    completionCleanupStarted = true;
+
+    await sleep(SEMANTIC_EXIT_GRACE_MS);
+    if (childClosed) return;
+
+    child.kill("SIGTERM");
+
+    await sleep(FORCED_EXIT_GRACE_MS);
+    if (childClosed) return;
+
+    child.kill("SIGKILL");
+  };
+
   const enqueue = (work) => {
     queue = queue.then(work, work);
     return queue;
@@ -98,6 +123,10 @@ async function runWrapper(meta, startedAt) {
       resolvedModel = normalized.model ?? resolvedModel;
       stopReason = normalized.stopReason ?? stopReason;
       usage = normalized.usage ?? usage;
+
+      if (normalized.stopReason) {
+        void forceChildExitAfterSemanticCompletion();
+      }
     }
   };
 
@@ -112,7 +141,7 @@ async function runWrapper(meta, startedAt) {
     childEnv.PI_SUBAGENTS_GITHUB_COPILOT_INITIATOR = "agent";
   }
 
-  const child = spawn("pi", args, {
+  child = spawn("pi", args, {
     cwd: meta.cwd,
     env: childEnv,
     stdio: ["ignore", "pipe", "pipe"],
@@ -151,10 +180,12 @@ async function runWrapper(meta, startedAt) {
 
     child.on("error", (error) => {
       spawnError = error;
+      childClosed = true;
       finish(1);
     });
 
     child.on("close", (code) => {
+      childClosed = true;
       finish(code ?? (spawnError ? 1 : 0));
     });
   });