Add incremental manifest-time code quality checks and JS duplicate method detection

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Co-Authored-By: Claude <noreply@anthropic.com>

app/RSpade/CodeQuality/Rules/CodeQualityRule_Abstract.php

@@ -92,6 +92,28 @@ abstract class CodeQualityRule_Abstract
     {
         return false;
     }
+
+    /**
+     * Whether this rule checks files incrementally or needs cross-file context
+     *
+     * This method is only relevant for rules where is_called_during_manifest_scan() = true.
+     *
+     * INCREMENTAL (true - default):
+     * - Rule checks each file independently
+     * - Only changed files are passed during incremental manifest rebuilds
+     * - More efficient for per-file validation rules
+     *
+     * CROSS-FILE (false):
+     * - Rule needs to see relationships between files or check the full manifest
+     * - Runs once per manifest build with access to all files via Manifest::get_all()
+     * - Use for rules that validate naming across files, check for duplicates, etc.
+     *
+     * @return bool True for per-file rules, false for cross-file rules
+     */
+    public function is_incremental(): bool
+    {
+        return true;
+    }
     
     /**
      * Get default severity for this rule