fix(create): show generated app name in hint line instead of input default

[srtaalej]

Changelog

Added an interactive name prompt to slack create. When no app name is provided via flag or argument, the CLI now prompts users to name their app, with a randomly generated name offered as a default. The InputPrompt method also now supports a Default option for pre-filling values. 🦋

Summary

This PR enables users to input an app name if one wasn't provided on slack create. Generated name can still be used by pressing Enter.

Test plan

• make test testdir=cmd/project testname=TestCreateCommand passes
• Manual: ./bin/slack create shows generated name in gray hint, input field is empty

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 61.53846% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.64%. Comparing base (ae1d9a0) to head (7c99f80).

Files with missing lines	Patch %	Lines
cmd/project/create.go	80.00%	1 Missing and 1 partial ⚠️
internal/pkg/create/create.go	0.00%	2 Missing ⚠️
internal/iostreams/survey.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #340      +/-   ##
==========================================
+ Coverage   64.63%   64.64%   +0.01%     
==========================================
  Files         212      212              
  Lines       17778    17789      +11     
==========================================
+ Hits        11491    11500       +9     
- Misses       5209     5211       +2     
  Partials     1078     1078              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.