fix: audit findings — test compilation, artifact pipeline, typo

- C-1: Add event_sender: None to ToolContext in file_write.rs and
  file_read.rs test helper functions (compilation fix)
- I-1: file_write tool now echoes content preview in output JSON,
  enabling streamStore.ts artifact auto-creation pipeline to work
- S-2: Fix typo "LLM 锥应错误" → "LLM 响应错误" in loop_runner.rs

crates/zclaw-runtime/src/loop_runner.rs

@@ -744,7 +744,7 @@ impl AgentLoop {
                         }
                         Ok(Some(Err(e))) => {
                             tracing::error!("[AgentLoop] Chunk error: {}", e);
-                            let _ = tx.send(LoopEvent::Error(format!("LLM 锥应错误: {}", e.to_string()))).await;
+                            let _ = tx.send(LoopEvent::Error(format!("LLM 响应错误: {}", e.to_string()))).await;
                             stream_errored = true;
                         }
                         Ok(None) => break, // Stream ended normally