feat(agents): add working summary tool feedback

[bogdanovich]

Summary

Add a working_summary tool feedback style for chat channels. This mode shows a compact temporary progress message such as:

Working...
• tool: `mcp_media_download_async`
• tool: `mcp_media_job_wait`

The message is edited in place while the turn is running and cleaned up when the final response is delivered. Tool names are rendered as code, and raw arguments/results are intentionally omitted to keep progress readable and avoid exposing sensitive values.

This complements the existing raw/default feedback style: existing behavior remains unchanged unless style is set to working_summary.

Follow-up fixes included

This PR also includes the feedback lifecycle fixes needed for long-running and subagent turns:

• scope Telegram feedback tracking by SessionKey, so a parent turn and subagent turn do not overwrite each other
• preserve session/topic metadata for async follow-up responses, so final responses clean up the correct progress message
• dismiss subagent-scoped feedback when an async subturn finishes
• label subagent progress messages, for example Deep Research working...
• add agents.defaults.tool_feedback.subagents so subagent feedback can be disabled independently while main-turn feedback stays enabled

The Telegram edit-rate throttling experiment is intentionally not included here; that should be a separate, configurable change if we upstream it.

Configuration

{
  "agents": {
    "defaults": {
      "tool_feedback": {
        "enabled": true,
        "style": "working_summary",
        "subagents": true
      }
    }
  }
}

Set subagents to false to keep main chat feedback visible while suppressing visible tool feedback from subagent turns. The default is true for backward compatibility.

Testing

• go test ./pkg/utils ./pkg/channels ./pkg/channels/telegram ./pkg/config ./pkg/agent