fix: correct path handling in SlnParser to ensure proper file resolution

[HandyS11]

This pull request makes a minor but important update to the way solution files are handled in the SlnParser. The method now ensures that the solution file path is always converted to a full path before parsing, which can help avoid issues with relative paths.

• Always resolves the provided path to a full path using fileSystem.GetFullPath before passing it to SolutionFile.Parse in the GetProjectPaths method of SlnParser.cs.

[Copilot]

Pull request overview

Updates SlnParser to normalize the input solution path to an absolute path before parsing, improving reliability when callers provide relative paths.

Changes:

• Resolve path via IFileSystem.GetFullPath before calling SolutionFile.Parse.
• Parse the solution using the normalized full path to ensure consistent project path resolution.

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