Improve exception handling documentation in Context.cs

Co-authored-by: Malcolmnixon <1863707+Malcolmnixon@users.noreply.github.com>

Author: Copilot

src/DemaConsulting.BuildMark/Context.cs

@@ -129,7 +129,9 @@ private void OpenLogFile(string logFile)
         {
             _logWriter = new StreamWriter(logFile, append: false);
         }
-        // Generic catch is justified here to wrap any file system exception with context
+        // Generic catch is justified here to wrap any file system exception with context.
+        // Expected exceptions include IOException, UnauthorizedAccessException, ArgumentException,
+        // NotSupportedException, and other file system-related exceptions.
         catch (Exception ex)
         {
             throw new InvalidOperationException($"Failed to open log file '{logFile}': {ex.Message}", ex);