This PR addresses an issue where PowerShell argument completers would fall back to file path completion when no valid argument matches were found, leading to irrelevant file and folder suggestions.

Problem

When using argument completion with GitHub PowerShell module commands, if no matches were found for the typed input, PowerShell would default to showing file and folder completions from the current directory. This created a confusing user experience where typing something like:

Get-GitHubLicense -Name invalidlicense<TAB>

Would show local files and folders instead of no completions, suggesting invalid options to the user.

Solution

Updated all 34 argument completers across 14 files to explicitly return $null when no matches are found. The fix follows this pattern:

Before:

Get-GitHubLicense @params | Where-Object { $_.Name -like $pattern } | ForEach-Object {
    [System.Management.Automation.CompletionResult]::new($_.Name, $_.Name, 'ParameterValue', $_.Name)
}

After:

$filteredOptions = Get-GitHubLicense @params | Where-Object { $_.Name -like $pattern }
if (-not $filteredOptions) {
    return $null
}
$filteredOptions | ForEach-Object {
    [System.Management.Automation.CompletionResult]::new($_.Name, $_.Name, 'ParameterValue', $_.Name)
}

Result

• ✅ When valid matches exist: Shows appropriate completions as before
• ✅ When no matches exist: No completions shown (cursor stays in place)
• ❌ Previously: Would show irrelevant file/folder completions when no matches found

This provides a cleaner, more intuitive completion experience that doesn't suggest invalid options to users.

Files Modified

All completer files throughout the module structure:

• Core completers in /src/completers.ps1
• Function-specific completers in /src/functions/public/*/completers.ps1

Fixes #514.

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