fix(runtime,hands): 搜索功能修复 — glm空参数回退+schema简化

根因: glm-5.1 不理解 oneOf+const 复杂 schema，发送 tool_calls 时
arguments 为空 {}。同时缺少从对话上下文提取用户意图的回退机制。

修复:
1. researcher input_schema 从 oneOf+const 改为扁平化属性 — glm 正确传参
2. loop_runner 增加 empty-input 回退 — 从最近用户消息注入 _fallback_query
3. researcher infer_action 增加 _fallback_query 分支处理
4. 调试日志降级 INFO→DEBUG (openai tool_calls delta, researcher input)

crates/zclaw-runtime/src/driver/openai.rs

@@ -208,7 +208,7 @@ impl LlmDriver for OpenAiDriver {
                             tracing::debug!("[OpenAI:stream] SSE #{}: {}", sse_event_count, &data[..data.len().min(300)]);
                         }
                         if data == "[DONE]" {
-                            tracing::debug!("[OpenAI:stream] Received [DONE], total SSE events: {}, raw bytes: {}", sse_event_count, raw_bytes_total);
+                            tracing::debug!("[OpenAI:stream] Received [DONE], total SSE events: {}, raw bytes: {}, tool_calls: {:?}", sse_event_count, raw_bytes_total, accumulated_tool_calls);
 
                             // Emit ToolUseEnd for all accumulated tool calls (skip invalid ones with empty name)
                             for (id, (name, args)) in &accumulated_tool_calls {
@@ -264,7 +264,7 @@ impl LlmDriver for OpenAiDriver {
 
                                     // Handle tool calls
                                     if let Some(tool_calls) = &delta.tool_calls {
-                                        tracing::trace!("[OpenAI] Received tool_calls delta: {:?}", tool_calls);
+                                        tracing::debug!("[OpenAI] Received tool_calls delta: {:?}", tool_calls);
                                         for tc in tool_calls {
                                             // Tool call start - has id and name
                                             if let Some(id) = &tc.id {