docs: fix missing api.proto import and clarify auto-registration

implement-a-customized-actuator (EN+ZH):
- Add the missing 'import "core/contract/math_contract.proto"' step in
  api.proto; without it the proto compiler cannot resolve SumContract in
  the InvokeSum RPC definition (compile failure)
- Add a note explaining that SumActuator must live in org.tron.core.actuator:
  TransactionRegister.registerActuator() uses Reflections to scan that
  package at startup and auto-registers every AbstractActuator subclass
  via the super() constructor call into TransactionFactory

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Little-Peony

docs/implement-a-customized-actuator-en.md

@@ -42,7 +42,13 @@ message Transaction {
 }
 ```
 
-Then register a function to ensure that gRPC can receive and identify the requests of this contract. Currently, gRPC protocols are all defined in `src/main/protos/api/api.proto`. To add an `InvokeSum` interface in Wallet Service:
+Then register a function to ensure that gRPC can receive and identify the requests of this contract. Currently, gRPC protocols are all defined in `src/main/protos/api/api.proto`. First add the import for the new proto file at the top of `api.proto`:
+
+```protobuf
+import "core/contract/math_contract.proto";
+```
+
+Then add an `InvokeSum` interface in the Wallet service:
 
 ```protobuf
 service Wallet {
@@ -76,6 +82,8 @@ After compilation, the corresponding .class under the java_out directory will be
 
 For now, the default Actuator supported by java-tron is located in `org.tron.core.actuator`. Creating `SumActuator` under this directory:
 
+> **Note**: The Actuator must be placed in the `org.tron.core.actuator` package. At node startup, `TransactionRegister.registerActuator()` uses reflection to scan that package and auto-discovers every `AbstractActuator` subclass. Each subclass is instantiated once (triggering the `super()` constructor which calls `TransactionFactory.register()`), so no manual registration code is needed.
+
 ```java
 import static org.tron.core.config.Parameter.ChainConstant.TRANSFER_FEE;
 

docs/implement-a-customized-actuator-zh.md

@@ -44,7 +44,13 @@ message Transaction {
 }
 ```
 
-然后还需要注册一个方法来保证 gRPC 能够接收并识别该类型合约的请求，目前 gRPC 协议统一定义在 src/main/protos/api/api.proto，在 api.proto 中的 Wallet Service 新增 `InvokeSum` 接口：
+然后还需要注册一个方法来保证 gRPC 能够接收并识别该类型合约的请求，目前 gRPC 协议统一定义在 src/main/protos/api/api.proto。首先在 `api.proto` 顶部添加对新 proto 文件的 import：
+
+```protobuf
+import "core/contract/math_contract.proto";
+```
+
+然后在 Wallet service 中新增 `InvokeSum` 接口：
 
 ```protobuf
 service Wallet {
@@ -78,6 +84,8 @@ protoc -I=src/main/protos/api -I=src/main/protos/core -I=src/main/protos  --java
 
 目前 java-tron 默认支持的 Actuator 存放在该模块的 org.tron.core.actuator 目录下，同样在该目录下创建 `SumActuator` ：
 
+> **注意**：Actuator 必须放在 `org.tron.core.actuator` 包下。节点启动时，`TransactionRegister.registerActuator()` 会通过反射扫描该包，自动发现所有 `AbstractActuator` 的子类，并各实例化一次（触发 `super()` 构造器，进而调用 `TransactionFactory.register()`）。因此无需手动编写注册代码。
+
 ```java
 import static org.tron.core.config.Parameter.ChainConstant.TRANSFER_FEE;