Bug Description

ACP sessions spawned via sessions_spawn({ runtime: "acp", mode: "run" }) never trigger the auto-announce flow to the parent session.

Root Cause (traced in source)

The announce system depends on lifecycle events with phase: "end":

1. Standard subagent runs go through runEmbeddedPiAgent → emits { stream: "lifecycle", phase: "end" } when done
2. The subagent registry listener (ensureListener in reply-*.js) picks up that event → calls completeSubagentRun → triggers runSubagentAnnounceFlow → announces to parent

ACP sessions take a different code path:

• ACP turns dispatch via tryDispatchAcpReply → acpManager.runTurn()
• When the ACP turn completes, it calls recordProcessed("completed") and markIdle("message_completed")
• It never emits the lifecycle event with phase: "end"
• So the subagent registry listener never fires → no announce

Expected Behavior

ACP sessions spawned with mode: "run" should auto-announce their completion to the parent session, just like standard subagent runs.

Reproduction

sessions_spawn({
  task: "echo hello",
  runtime: "acp",
  agentId: "claude",
  mode: "run",
  thread: true
})

The session completes but no announce message appears in the parent session or Discord channel.

Environment

• OpenClaw: v2026.3.7
• acpx: v0.1.15
• Node: 22.19.0
• OS: macOS (arm64)

Suggested Fix

In tryDispatchAcpReply (src/auto-reply/reply/dispatch-acp.ts), after acpManager.runTurn() completes successfully, emit:

emitAgentEvent({
  runId,
  stream: "lifecycle",
  data: {
    phase: "end",
    endedAt: Date.now()
  }
});

This would connect the ACP completion to the existing announce pipeline.

Workaround

Parent agent manually announces via message(action=send) after detecting ACP completion through streamTo: "parent" system events.