fix: restore subagent tool call notifications after summon refactor

[rabi]

Summary

The move of subagents into the summon extension broke notification forwarding -- subagent tool calls were no longer visible in CLI/UI.

Plumb notification forwarding from subagent tasks through the summon extension so tool calls are visible in CLI/UI. For async delegates, buffer notifications per-task and drain when load(taskId) is called.

Type of Change

• Feature
• Bug fix
• Refactor / Code quality
• Performance improvement
• Documentation
• Tests
• Security fix
• Build / Release
• Other (specify below)

AI Assistance

• This PR was created or reviewed with AI assistance

Testing

Tested locally.

Screenshots/Demos (for UX changes)

After:

  ● new session · gcp_vertex_ai claude-opus-4-6
    20260216_1 · /home/ramishra/work/LLM/goose

🪿 goose ready — type a message to get started

  ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ 0% 0/200k
🪿 Use subagents to do these tasks in parallel:
1. Get last 20 pull requests from vllm-project/vllm
2. Get last 20 pull requests from sgl-project/sglang

Run them concurrently, then analyze the results for similarity, list all PRs and explan similarity


I'll fetch the last 20 PRs from both repositories concurrently using subagents.
  ▸ delegate
    instructions Get the last 20 pull requests from the vllm-project/vllm repository on GitHub. List all of them w...
    async: true


  ▸ delegate
    instructions Get the last 20 pull requests from the sgl-project/sglang repository on GitHub. List all of them ...
    async: true

Both tasks are running in the background. Let me wait for their results now.
  ▸ [subagent:3] list_pull_requests | github
    owner: sgl-project
    repo: sglang
    state: all
    sort: created
    direction: desc
    perPage: 20


  ▸ [subagent:2] list_pull_requests | github
    owner: vllm-project
    repo: vllm
    state: all
    sort: created
    direction: desc
    perPage: 20


  ▸ [subagent:3] shell | developer
    command: cat /tmp/goose_mcp_responses/mcp_response_20260216_045207.665871.txt | python3 -c "
import json, sys
data = json.load(sys.stdin)
for pr in data:
    print(f\"{pr['number']}|{pr['title']}|{pr['user...


  ▸ [subagent:2] shell | developer
    command: cat /tmp/goose_mcp_responses/mcp_response_20260216_045208.924131.txt | python3 -c "
import json, sys
data = json.load(sys.stdin)
for pr in data:
    number = pr['number']
    title = pr['title']
 

Both results are in. Here's the full analysis: