write_file 入参形状校验收进 write_file_input，MCP 预检不再漏掉未知字段

- 其它 *_input 解析器都先调 ToolArgumentsRejection::check，只有 write_file_input 没有；工具桥路径靠 bridge_write_file_with_permit 里另一次 check 兜住，但独立客户端 MCP 预检 validate_write_file_arguments 只调 write_file_input，带未知字段的入参能通过预检、要等回客户端桥才被拒
- 在 write_file_input 开头补上同一份 check（path/content 白名单），两个入口共用一条规则；写文件门禁里的那次 check 保留，保证「先查形状、再过权限」的现有顺序不变
- 测试补一条：{"path":"game/index.html","content":"…","unexpected":1} 必须被 validate_write_file_arguments 拒绝

验证：cargo test --bin genarrative-ai-game-creator-shell -- agent::direct_tool_bridge:: 40 passed；agent::direct_tools_mcp::tests::tool_catalog_preserves_reviewed_resource_contracts 通过

apps/ai-game-creator-shell/src-tauri/src/agent/direct_tool_bridge.rs

@@ -1718,6 +1718,7 @@ fn bridge_file_content_changed(root: &Path, path: &str, content: &[u8]) -> Optio
 pub(in crate::agent) fn write_file_input(
     arguments: &Value,
 ) -> Result<(String, String), WriteFileError> {
+    ToolArgumentsRejection::check(arguments, &["path", "content"])?;
     let raw_path = arguments
         .get("path")
         .and_then(Value::as_str)

apps/ai-game-creator-shell/src-tauri/src/agent/direct_tools_mcp.rs

@@ -2849,6 +2849,12 @@ mod tests {
             "content": "{}"
         }))
         .is_err());
+        assert!(validate_write_file_arguments(&json!({
+            "path": "game/index.html",
+            "content": "<html></html>",
+            "unexpected": 1
+        }))
+        .is_err());
         assert_eq!(
             direct_tool_bridge::prepare_game_art_input(&json!({ "brief": "美术包" }))
                 .expect("safe default")