fix: graceful shutdown for subcontainer daemons

Two issues fixed:

1. Process group cascade: exec-command processes inherited the
   container runtime's process group. When an entrypoint script
   did kill(0, SIGTERM) during shutdown, it signaled ALL processes
   in the group — including other subcontainers' launch wrappers,
   causing their PID namespaces to collapse. Fixed by calling
   setsid() in exec-command's pre_exec to isolate each service
   in its own process group.

2. Unordered daemon termination: removeChild("main") fired
   onLeaveContext callbacks for all Daemon.of() instances
   simultaneously, bypassing Daemons.term()'s reverse-dependency
   ordering. Fixed by having Daemons.build() mark individual
   daemons as managed (suppressing their onLeaveContext) and
   registering a single onLeaveContext that calls the ordered
   Daemons.term(). The term() method is deduplicated so
   system.stop() and onLeaveContext share the same shutdown.

core/src/service/effects/subcontainer/sync.rs

@@ -283,6 +283,10 @@ impl ExecParams {
             let set_gid = gid.ok();
             unsafe {
                 cmd.pre_exec(move || {
+                    // Create a new process group so entrypoint scripts that do
+                    // kill(0, SIGTERM) don't cascade to other subcontainers.
+                    nix::unistd::setsid()
+                        .map_err(|e| std::io::Error::from_raw_os_error(e as i32))?;
                     if !groups.is_empty() {
                         nix::unistd::setgroups(&groups)
                             .map_err(|e| std::io::Error::from_raw_os_error(e as i32))?;

sdk/package/lib/mainFn/Daemon.ts

@@ -27,6 +27,7 @@ export class Daemon<
   protected exitedSuccess = false
   private onExitFns: ((success: boolean) => void)[] = []
   private loop: { abort: AbortController; done: Promise<void> } | null = null
+  private _managed = false
   protected constructor(
     private subcontainer: C,
     private startCommand: () => Promise<CommandController<Manifest, C>>,
@@ -42,7 +43,8 @@ export class Daemon<
    * Factory method to create a new Daemon.
    *
    * Returns a curried function: `(effects, subcontainer, exec) => Daemon`.
-   * The daemon auto-terminates when the effects context is left.
+   * Registers an `onLeaveContext` callback that terminates the daemon when the
+   * effects context is left.
    */
   static of<Manifest extends T.SDKManifest>() {
     return <C extends SubContainer<Manifest> | null>(
@@ -60,7 +62,9 @@ export class Daemon<
         )
       const res = new Daemon(subc, startCommand)
       effects.onLeaveContext(() => {
+        if (!res._managed) {
           res.term({ destroySubcontainer: true }).catch((e) => logErrorOnce(e))
+        }
       })
       return res
     }
@@ -173,6 +177,14 @@ export class Daemon<
       await this.subcontainer?.destroy()
     }
   }
+  /**
+   * Mark this daemon as managed by a {@link Daemons} instance.
+   * Suppresses the individual `onLeaveContext` termination since the
+   * `Daemons` instance handles ordered shutdown.
+   */
+  markManaged() {
+    this._managed = true
+  }
   /** Get a reference-counted handle to the daemon's subcontainer, or null if there is none */
   subcontainerRc(): SubContainerRc<Manifest> | null {
     return this.subcontainer?.rc() ?? null

sdk/package/lib/mainFn/Daemons.ts

@@ -176,6 +176,7 @@ Daemons.of({
 export class Daemons<Manifest extends T.SDKManifest, Ids extends string>
   implements T.DaemonBuildable
 {
+  private termPromise: Promise<void> | null = null
   private constructor(
     readonly effects: T.Effects,
     readonly ids: Ids[],
@@ -413,6 +414,13 @@ export class Daemons<Manifest extends T.SDKManifest, Ids extends string>
    * if a dependency cycle is detected.
    */
   async term() {
+    if (!this.termPromise) {
+      this.termPromise = this._term()
+    }
+    return this.termPromise
+  }
+
+  private async _term() {
     const remaining = new Set(this.healthDaemons)
 
     while (remaining.size > 0) {
@@ -459,7 +467,11 @@ export class Daemons<Manifest extends T.SDKManifest, Ids extends string>
    * @returns This `Daemons` instance, now running
    */
   async build() {
+    this.effects.onLeaveContext(() => {
+      this.term().catch((e) => console.error(e))
+    })
     for (const daemon of this.healthDaemons) {
+      daemon.daemon?.markManaged()
       await daemon.updateStatus()
     }
     return this