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 65.05%. Comparing base (c449532) to head (bbba8d6).

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%   65.05%   -0.02%     
==========================================
  Files         215      216       +1     
  Lines       18179    18231      +52     
==========================================
+ Hits        11829    11860      +31     
- Misses       5254     5273      +19     
- Partials     1096     1098       +2     

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[mwbrooks]

🎉 Love the video and this is looking good!

🧪 I'll manually test this shortly, but wanted to share some quick feedback. I noticed that the patch test coverage is 50%. It would be nice to get that around 70% to keep our code coverage increasing slightly. I've left one comment that might allow us to boost the test coverage.

[mwbrooks]

question: Do we need this testing override? We are trying to remove this pattern and a glance at charmPromptTemplateSelection looks like we can test this function safely since clients and clients.IO have mocks available. 🤞🏻