fix(kernel): 使用 Kernel 配置的 model 而非 Agent 持久化的旧值

问题：在"模型与 API"页面切换模型后，对话仍使用旧模型
根因：Agent 配置从数据库恢复，其 model 字段优先于 Kernel 配置

修复：
- kernel.rs: send_message/send_message_stream 始终使用 Kernel 的当前 model
- openai.rs: 添加 User-Agent header 解决 Coding Plan API 405 错误
- kernel_commands.rs: 添加详细调试日志便于追踪配置传递
- troubleshooting.md: 记录此问题的排查过程和解决方案

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

crates/zclaw-kernel/src/kernel.rs

@@ -109,20 +109,36 @@ impl Kernel {
 
     /// Send a message to an agent
     pub async fn send_message(&self, agent_id: &AgentId, message: String) -> Result<MessageResponse> {
-        let _agent = self.registry.get(agent_id)
+        let agent_config = self.registry.get(agent_id)
             .ok_or_else(|| zclaw_types::ZclawError::NotFound(format!("Agent not found: {}", agent_id)))?;
 
         // Create or get session
         let session_id = self.memory.create_session(agent_id).await?;
 
-        // Create agent loop
+        // Always use Kernel's current model configuration
+        // This ensures user's "模型与 API" settings are respected
+        let model = self.config.model().to_string();
+
+        eprintln!("[Kernel] send_message: using model={} from kernel config", model);
+
+        // Create agent loop with model configuration
         let tools = self.create_tool_registry();
         let loop_runner = AgentLoop::new(
             *agent_id,
             self.driver.clone(),
             tools,
             self.memory.clone(),
-        );
+        )
+        .with_model(&model)
+        .with_max_tokens(agent_config.max_tokens.unwrap_or_else(|| self.config.max_tokens()))
+        .with_temperature(agent_config.temperature.unwrap_or_else(|| self.config.temperature()));
+
+        // Add system prompt if configured
+        let loop_runner = if let Some(ref prompt) = agent_config.system_prompt {
+            loop_runner.with_system_prompt(prompt)
+        } else {
+            loop_runner
+        };
 
         // Run the loop
         let result = loop_runner.run(session_id, message).await?;
@@ -140,20 +156,36 @@ impl Kernel {
         agent_id: &AgentId,
         message: String,
     ) -> Result<mpsc::Receiver<zclaw_runtime::LoopEvent>> {
-        let _agent = self.registry.get(agent_id)
+        let agent_config = self.registry.get(agent_id)
             .ok_or_else(|| zclaw_types::ZclawError::NotFound(format!("Agent not found: {}", agent_id)))?;
 
         // Create session
         let session_id = self.memory.create_session(agent_id).await?;
 
-        // Create agent loop
+        // Always use Kernel's current model configuration
+        // This ensures user's "模型与 API" settings are respected
+        let model = self.config.model().to_string();
+
+        eprintln!("[Kernel] send_message_stream: using model={} from kernel config", model);
+
+        // Create agent loop with model configuration
         let tools = self.create_tool_registry();
         let loop_runner = AgentLoop::new(
             *agent_id,
             self.driver.clone(),
             tools,
             self.memory.clone(),
-        );
+        )
+        .with_model(&model)
+        .with_max_tokens(agent_config.max_tokens.unwrap_or_else(|| self.config.max_tokens()))
+        .with_temperature(agent_config.temperature.unwrap_or_else(|| self.config.temperature()));
+
+        // Add system prompt if configured
+        let loop_runner = if let Some(ref prompt) = agent_config.system_prompt {
+            loop_runner.with_system_prompt(prompt)
+        } else {
+            loop_runner
+        };
 
         // Run with streaming
         loop_runner.run_streaming(session_id, message).await
@@ -169,6 +201,11 @@ impl Kernel {
         self.events.publish(Event::KernelShutdown);
         Ok(())
     }
+
+    /// Get the kernel configuration
+    pub fn config(&self) -> &KernelConfig {
+        &self.config
+    }
 }
 
 /// Response from sending a message