feat: accept chunks as arguments to chat stream helper

[srtaalej]

Summary

This PR enables chunks processing in the chat stream helper

    const streamer = new ChatStreamer(client, client.logger, {
      channel: CHANNEL_ID,
      thread_ts: threadTs,
      recipient_team_id: 'TEAM_ID,
      recipient_user_id: 'USER_ID',
    }, { buffer_size: 1 });

    await streamer.append({
      chunks: [
        {
          type: 'markdown_text',
          text: '**Hello!** I am starting to process your request...\n\n'
        }]
    });

    await streamer.stop({
      chunks: [
        {
          type: 'markdown_text',
          text: '\n\n---\n\n✅ **All tasks completed successfully!**\n',
        },
        {
          type: 'markdown_text',
          text: 'Thank you for using the streaming API with chunks.',
        },
      ],
    });

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.09%. Comparing base (b44cee1) to head (eb8b462).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                       Coverage Diff                       @@
##           feat-ai-apps-thinking-steps    #2470      +/-   ##
===============================================================
- Coverage                        93.09%   93.09%   -0.01%     
===============================================================
  Files                               40       40              
  Lines                            11240    11233       -7     
  Branches                           713      712       -1     
===============================================================
- Hits                             10464    10457       -7     
  Misses                             764      764              
  Partials                            12       12              

Flag	Coverage Δ
cli-hooks	95.23% <ø> (ø)
cli-test	94.79% <ø> (ø)
webhook	96.66% <ø> (ø)

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[mwbrooks]

🙌🏻 Exciting, thanks for opening this PR @srtaalej!

It looks like you've also added the new task_update check along with the plan_update 😄

🧪 @zimeg and I will take a look at the PR soon. In the meantime, it looks like there are some failed tests that will need to be resolved.