feat(plugins): add preserve_autoload option for PHP plugin configuration

When PHP linter extensions like Larastan bootstrap the Laravel
application, they need the project's PSR-4 namespace mappings in the
sandbox autoloader. Previously, filter_composer unconditionally stripped
autoload/autoload-dev sections, causing "Class not found" crashes.

This adds a preserve_autoload boolean (default false) that, when
enabled, preserves autoload sections and creates symlinks from the
sandbox to the project root so Composer's generated autoloader resolves
paths to the actual source files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sinemacula-ben

qlty-check/src/planner/config.rs

@@ -175,11 +175,13 @@ fn configure_plugin(
             }
 
             plugin_def.package_file = Some(package_file.to_str().unwrap_or_default().to_string());
+            plugin_def.workspace_root = Some(prefixed_root);
         }
 
         // This is becoming a weird pattern, we should probably refactor this?
         plugin_def.fetch = enabled_plugin.fetch.clone();
         plugin_def.package_filters = enabled_plugin.package_filters.clone();
+        plugin_def.preserve_autoload = enabled_plugin.preserve_autoload;
         plugin_def.prefix = enabled_plugin.prefix.clone();
 
         plugin_def