feat: add --accessible flag to huh interactive prompts

[srtaalej]

Changelog

Added --accessible flag for screen reader friendly prompts

Summary

Related: #454
This PR adds a global --accessible flag that switches huh interactive prompts to accessible mode. In accessible mode, select prompts render as numbered lists with "Enter a number between 1 and N" input, confirm prompts accept y/n text, and input prompts use plain line-by-line I/O. This makes the CLI usable with screen readers by avoiding the TUI-based rendering

Test plan

Run slack create --accessible and verify prompts render as numbered lists
Run slack login --accessible and verify confirm prompt accepts y/n
Run slack create (without flag) and verify normal TUI prompts still work
go test ./internal/iostreams/ -run TestFormsAccessible

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 60.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.05%. Comparing base (5100c02) to head (f39d175).

Files with missing lines	Patch %	Lines
cmd/root.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #455      +/-   ##
==========================================
- Coverage   71.06%   71.05%   -0.02%     
==========================================
  Files         220      220              
  Lines       18522    18527       +5     
==========================================
+ Hits        13163    13164       +1     
+ Misses       4181     4180       -1     
- Partials     1178     1183       +5     

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[zimeg]

@srtaalej So amazing to find this feature arriving here! 🍀 ✨

Before approving I want to leave a few comments, but think we can follow up with some other improvements to the edges:

• Environment Variable: The ACCESSIBLE environment variable is standard I understand and we should include support alongside these changes! This makes preferring these prompts easier with an export added to the shell profile 🔬
• Blank Selections: The "select" prompts request a number to be entered but accept blank input for the first option! This might be an upstream issue 🐛
• Input Default: Adjacent for the "input" prompt I find the default value of the create command name isn't showing 🧪

The first note is most important for these changes IMHO! I'd be curious if the latter two can be proven in unit tests, but please don't consider those blocking 🙏

[zimeg]

Suggested change

	func Test_AccessibleImpliesNoColor(t *testing.T) {
	cfg := &config.Config{Accessible: true}
	// Simulate the logic from PersistentPreRunE
	if cfg.Accessible {
	cfg.NoColor = true
	}
	assert.True(t, cfg.NoColor, "--accessible should imply --no-color")
	}

🪓 note: I'm not sure this test is so useful against regressions here?

[zimeg]

🌲 thought: As we're introducing this, should we include the environment variable similar?

ACCESSIBLE

We recommend setting this through an environment variable or configuration option to allow the user to control accessibility.

🔗 https://github.com/charmbracelet/huh?tab=readme-ov-file#accessibility

[zimeg]

🔍 ramble: We might find this adjacent file most useful!

slack-cli/internal/config/dotenv.go

Lines 23 to 24 in f39d175

	// LoadEnvironmentVariables sets flags based on their environment variable value
	func (c *Config) LoadEnvironmentVariables() error {