Fix command line relative path resolution

[Copilot]

Command line arguments with relative paths (e.g., quicklook 1.txt) failed when invoked from directories other than the QuickLook installation directory. File.Exists() and Directory.Exists() were checking paths against the application's working directory instead of the shell's current directory.

Changes

• Convert relative paths to absolute using Path.GetFullPath() before existence checks in both first and second instance code paths
• Add specific exception handling for ArgumentException, SecurityException, NotSupportedException, and PathTooLongException

// Before
if (e.Args.Any() && (Directory.Exists(e.Args.First()) || File.Exists(e.Args.First())))
    PipeServerManager.SendMessage(PipeMessages.Toggle, e.Args.First());

// After
if (e.Args.Any())
{
    try
    {
        var path = Path.GetFullPath(e.Args.First());
        if (Directory.Exists(path) || File.Exists(path))
            PipeServerManager.SendMessage(PipeMessages.Toggle, path);
    }
    catch (Exception ex) when (ex is ArgumentException || ex is SecurityException || 
                               ex is NotSupportedException || ex is PathTooLongException)
    {
        // Invalid path, ignore
    }
}

Absolute paths continue to work unchanged. Invalid paths are silently ignored.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Command line only works with absolute path</issue_title>
<issue_description>Describe the bug

2026-01-13.214436.mp4

As the video shows:

• Using relative path quicklook 1.txt does nothing.
• Using absolute path quicklook D:/test/1.txt shows preview.
• When I change current dir to QuickLook program folder, these two ways both work.

To Reproduce
Follow my video.

Expected behavior
Relative path also works.

Desktop (please complete the following information):

• OS Version: Windows 11 PRO 25H2 26200.7462
• QuickLook Version: 4.4.0 from EXE installer
  </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Command line only works with absolute path #1856

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