fix: Properly escape file path in chmod command (#1527) (#1732)

The chmod command was constructed with an unsanitized file path which
could fail or be dangerous with special characters. This change wraps
the path in single quotes and escapes any embedded single quotes with
the standard '\'' technique.

Fixes #1527

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: thomhurst

src/ModularPipelines/Context/FileInstaller.cs

@@ -28,7 +28,8 @@ public virtual async Task<CommandResult> InstallFromFileAsync(InstallerOptions o
             }, cancellationToken).ConfigureAwait(false);
         }
 
-        await _bash.Command(new BashCommandOptions($"chmod u+x {options.Path}"), cancellationToken).ConfigureAwait(false);
+        var escapedPath = options.Path.Replace("'", "'\\''");
+        await _bash.Command(new BashCommandOptions($"chmod u+x '{escapedPath}'"), cancellationToken).ConfigureAwait(false);
 
         return await _bash.FromFile(new BashFileOptions(options.Path), cancellationToken).ConfigureAwait(false);
     }