feat(charm): adds 'huh' dynamic forms to create command

[srtaalej]

Changelog

When the charm experiment is enabled, slack create now presents a single interactive form for selecting both the app category and language template, with options that update dynamically as you navigate. 🦋

Summary

This PR replaces the survey-based two-step category/template prompt with a single-screen 'huh' form when the charm experiment is enabled. Category and language selects render together; changing the category dynamically updates the template options via OptionsFunc.

Screen.Recording.2026-03-03.at.1.18.47.PM.mov

Testing

• make build — 0 issues
• make test — all tests pass
• ./bin/slack create --experiment=charm — form renders with category and template on one screen; changing category updates template options; "View more samples" shows browse option

Requirements

• 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

❌ Patch coverage is 50.00000% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.98%. Comparing base (1e7cf7f) to head (f514974).

Files with missing lines	Patch %	Lines
cmd/project/create_template_charm.go	52.27%	21 Missing ⚠️
cmd/project/create_template.go	37.50%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #362      +/-   ##
==========================================
- Coverage   65.06%   64.98%   -0.09%     
==========================================
  Files         215      216       +1     
  Lines       18179    18231      +52     
==========================================
+ Hits        11829    11848      +19     
- Misses       5254     5282      +28     
- Partials     1096     1101       +5     

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