fix(app): implement helper for Windows app existence check using where.exe

[OpeOginni]

What does this PR do?

Implements the helper to check if an app exists on the windows machine, used in the display of different apps one can open from on the desktop app.

Best to test using the application set for windows https://github.com/anomalyco/opencode/blob/dev/packages/app/src/components/session/session-header.tsx#L88

How did you verify your code works?

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

I found one potentially related PR:

• PR feat(desktop): filter Open In list to only show installed apps #12454: "feat(desktop): filter Open In list to only show installed apps"
  • This appears related because it's also about filtering/checking which apps are installed to show in the desktop UI, which aligns with the purpose of your PR fix(app): implement helper for Windows app existence check using where.exe #13039 (checking app existence for display purposes)

However, PR #13039 is the current PR you're checking, so the only other potentially related work is PR #12454, which may or may not be addressing the same functionality from a different angle.