Reduce scope of regex in PowerShellExeFinder

[tsmarvin]

PR Summary

• Update integer checking regex to match implied expectations from related comments.
  • While reading through the comments associated with the IntRegex value it is implied that we're only looking for single digit integer folders. This update formally matches that implied expectation.

PR Checklist

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[Copilot]

Pull Request Overview

This PR updates the integer checking regex in the PowerShellExeFinder to enforce a stricter validation by matching exactly a single digit rather than one or more digits.

• Change the IntRegex from matching one or more digits (/^\d+$/) to exactly one digit (/^\d$/).
• This adjustment aligns the implementation with the implied expectation from related comments regarding folder naming.

Comments suppressed due to low confidence (1)

src/platform.ts:81

• Consider updating the associated comment to clearly state that the regex now only supports single digit folder names, ensuring that the documentation is consistent with the updated regex behavior.

    private static IntRegex = /^\d$/;