fix(desktop): stop dev app surviving its terminal

Electron was detached from the desktop runner, allowing it to outlive a stopped workspace terminal with broken output pipes and retain the single-instance lock. Keep Electron owned by the runner and preserve explicit process-group cleanup for detached child trees.

docs/development.md

@@ -115,6 +115,10 @@ desktop-only environment inherited by terminals opened inside Paseo from couplin
 a new worktree instance to the parent desktop instance's profile or single-instance
 lock.
 
+Electron remains in the desktop dev runner's process group. Closing or stopping the
+workspace-script terminal must terminate Electron with Metro; detaching Electron
+leaves an orphan holding the worktree's single-instance lock and broken output pipes.
+
 With desktop dev running, verify the real BrowserWindow, titlebar clearance, fullscreen
 transition, and 751-pixel settings split with:
 

packages/desktop/scripts/dev-runner-config.mjs

@@ -0,0 +1,17 @@
+export function createElectronSpawnOptions({ env, colorEnv, expoDevUrl }) {
+  return {
+    // Electron must stay in the runner's process group. Paseo workspace scripts
+    // own the terminal process group, so detaching Electron lets it survive a
+    // service stop with broken stdout/stderr pipes and block the next launch.
+    detached: false,
+    env: {
+      ...env,
+      ...colorEnv,
+      EXPO_DEV_URL: expoDevUrl,
+    },
+  };
+}
+
+export function resolveChildKillTarget(pid, detached) {
+  return detached ? -pid : pid;
+}

packages/desktop/scripts/dev-runner-config.test.mjs

@@ -0,0 +1,26 @@
+import { describe, expect, test } from "vitest";
+import { createElectronSpawnOptions, resolveChildKillTarget } from "./dev-runner-config.mjs";
+
+describe("desktop dev process ownership", () => {
+  test("keeps Electron in the runner process group", () => {
+    const options = createElectronSpawnOptions({
+      env: { PATH: "/usr/bin" },
+      colorEnv: { FORCE_COLOR: "1" },
+      expoDevUrl: "http://localhost:8082",
+    });
+
+    expect(options).toMatchObject({
+      detached: false,
+      env: {
+        PATH: "/usr/bin",
+        FORCE_COLOR: "1",
+        EXPO_DEV_URL: "http://localhost:8082",
+      },
+    });
+  });
+
+  test("targets the whole process group for detached child trees", () => {
+    expect(resolveChildKillTarget(42, true)).toBe(-42);
+    expect(resolveChildKillTarget(42, false)).toBe(42);
+  });
+});

packages/desktop/scripts/dev-runner.mjs

@@ -4,6 +4,7 @@ import path from "node:path";
 import { spawn } from "node:child_process";
 import { createRequire } from "node:module";
 import { fileURLToPath } from "node:url";
+import { createElectronSpawnOptions, resolveChildKillTarget } from "./dev-runner-config.mjs";
 
 const scriptDir = path.dirname(fileURLToPath(import.meta.url));
 const desktopDir = path.resolve(scriptDir, "..");
@@ -58,7 +59,11 @@ function spawnChild(name, command, args, options = {}) {
     ...options,
   });
 
-  children.set(name, child);
+  const managedChild = {
+    process: child,
+    detached: options.detached === true,
+  };
+  children.set(name, managedChild);
   prefixStream(name, child.stdout, process.stdout);
   prefixStream(name, child.stderr, process.stderr);
 
@@ -82,17 +87,13 @@ function spawnChild(name, command, args, options = {}) {
   return child;
 }
 
-function killChild(child, signal) {
+function killChild({ process: child, detached }, signal) {
   if (!child.pid || child.killed) {
     return;
   }
 
   try {
-    if (child.detached) {
-      process.kill(-child.pid, signal);
-    } else {
-      child.kill(signal);
-    }
+    process.kill(resolveChildKillTarget(child.pid, detached), signal);
   } catch {
     // The child may have exited between the liveness check and the signal.
   }
@@ -176,12 +177,14 @@ try {
 }
 
 if (!stopping) {
-  spawnChild("electron", electron, [...electronArgs, desktopDir], {
-    detached: true,
-    env: {
-      ...process.env,
-      ...colorEnv,
-      EXPO_DEV_URL: expoDevUrl,
-    },
-  });
+  spawnChild(
+    "electron",
+    electron,
+    [...electronArgs, desktopDir],
+    createElectronSpawnOptions({
+      env: process.env,
+      colorEnv,
+      expoDevUrl,
+    }),
+  );
 }