feat: add task_card and plan_blocks

[srtaalej]

Summary

This PR adds the task_card block and the plan block for usage in standalone messages.

⚠️ This is experimental and requires a toggle to preview!

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 (27478ff).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                       Coverage Diff                       @@
##           feat-ai-apps-thinking-steps    #2471      +/-   ##
===============================================================
- 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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