feat: make policy length limits configurable per engine (#624)

- Add PolicyLengthConfig struct with max_col, max_file_bytes, and
  max_lines fields, replacing hardcoded constants in the lexer.
- Add Engine::set_policy_length_config and clear_policy_length_config
  to allow callers to override the default limits.
- Add Source::from_contents_with_limits and from_file_with_limits for
  direct Source construction with custom limits; existing from_contents
  and from_file signatures are preserved using defaults.
- Add tests for default rejection, custom limits, and engine plumbing.
- Add bindings for C, C++, Python, WASM/JS, Java, Ruby, C#, Go

bindings/csharp/Regorus/Engine.cs

@@ -82,6 +82,24 @@ namespace Regorus
                 CheckAndDropResult(Regorus.Internal.API.regorus_engine_clear_execution_timer_config((Regorus.Internal.RegorusEngine*)enginePtr));
             });
         }
+
+        public void SetPolicyLengthConfig(PolicyLengthConfig config)
+        {
+            var nativeConfig = config.ToNative();
+            UseHandle(enginePtr =>
+            {
+                CheckAndDropResult(Regorus.Internal.API.regorus_engine_set_policy_length_config((Regorus.Internal.RegorusEngine*)enginePtr, nativeConfig));
+            });
+        }
+
+        public void ClearPolicyLengthConfig()
+        {
+            UseHandle(enginePtr =>
+            {
+                CheckAndDropResult(Regorus.Internal.API.regorus_engine_clear_policy_length_config((Regorus.Internal.RegorusEngine*)enginePtr));
+            });
+        }
+
         public string? AddPolicy(string path, string rego)
         {
             return Utf8Marshaller.WithUtf8(path, pathPtr =>