refactor: 重构 CallCommand 类并优化文档注释

- 重新组织类文档，增加对 CallCommand 功能和行为的详细描述
- 添加 execute 方法的详细注释，明确参数和返回值的用途
- 优化代码结构，提高可读性和可维护性

src/main/java/org/jcnc/snow/vm/commands/flow/control/CallCommand.java

@@ -5,12 +5,48 @@ import org.jcnc.snow.vm.interfaces.Command;
 import org.jcnc.snow.vm.module.*;
 
 /**
- * CALL addr nArgs — pushes a new stack-frame, transfers the specified
- * argument count from the operand stack into the callee’s local slots
- * 0‥n-1 (left-to-right), then jumps to {@code addr}.
+ * The CallCommand class implements the {@link Command} interface and represents a subroutine/function call
+ * instruction in the virtual machine.
+ * <p>
+ * This command facilitates method invocation by creating a new stack frame, transferring arguments
+ * from the operand stack to the callee's local variable store, and jumping to the specified target address.
+ * </p>
+ *
+ * <p>Specific behavior:</p>
+ * <ul>
+ *     <li>Parses the target address and the number of arguments from the instruction parameters.</li>
+ *     <li>Validates the operands and checks for correct argument count.</li>
+ *     <li>Builds a new local variable store for the callee and transfers arguments from the operand stack
+ *         (left-to-right order, where the top of the stack is the last argument).</li>
+ *     <li>Pushes a new stack frame onto the call stack, saving the return address and local variables.</li>
+ *     <li>Jumps to the specified target address to begin execution of the callee function.</li>
+ *     <li>If any error occurs (e.g., malformed operands, stack underflow), an exception is thrown.</li>
+ * </ul>
  */
 public class CallCommand implements Command {
 
+    /**
+     * Executes the CALL instruction, initiating a subroutine/function call within the virtual machine.
+     * <p>
+     * This method handles the creation of a new stack frame for the callee, argument passing,
+     * and control transfer to the target function address.
+     * </p>
+     *
+     * @param parts         The instruction parameters. Must include:
+     *                      <ul>
+     *                          <li>{@code parts[0]}: The "CALL" operator.</li>
+     *                          <li>{@code parts[1]}: The target address of the callee function.</li>
+     *                          <li>{@code parts[2]}: The number of arguments to pass.</li>
+     *                      </ul>
+     * @param currentPC     The current program counter, used to record the return address for after the call.
+     * @param operandStack  The operand stack manager. Arguments are popped from this stack.
+     * @param callerLVS     The local variable store of the caller function (not directly modified here).
+     * @param callStack     The virtual machine's call stack manager, used to push the new stack frame.
+     * @return The new program counter value, which is the address of the callee function (i.e., jump target).
+     *         The VM should transfer control to this address after setting up the call frame.
+     * @throws IllegalArgumentException If the instruction parameters are malformed or missing.
+     * @throws IllegalStateException    If the operand stack does not contain enough arguments.
+     */
     @Override
     public int execute(String[] parts,
                        int currentPC,