refactor(crates): kernel/generation module split + DeerFlow optimizations + middleware + dead code cleanup

- Split zclaw-kernel/kernel.rs (1486 lines) into 9 domain modules
- Split zclaw-kernel/generation.rs (1080 lines) into 3 modules
- Add DeerFlow-inspired middleware: DanglingTool, SubagentLimit, ToolError, ToolOutputGuard
- Add PromptBuilder for structured system prompt assembly
- Add FactStore (zclaw-memory) for persistent fact extraction
- Add task builtin tool for agent task management
- Driver improvements: Anthropic/OpenAI extended thinking, Gemini safety settings
- Replace let _ = with proper log::warn! across SaaS handlers
- Remove unused dependency (url) from zclaw-hands

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

@@ -58,6 +58,10 @@ impl LocalDriver {
     // ----------------------------------------------------------------
 
     fn build_api_request(&self, request: &CompletionRequest) -> LocalApiRequest {
+        if request.thinking_enabled {
+            tracing::debug!("[LocalDriver] thinking_enabled=true but local driver does not support native thinking mode; ignoring");
+        }
+
         let messages: Vec<LocalApiMessage> = request
             .messages
             .iter()
@@ -183,7 +187,7 @@ impl LocalDriver {
                     .unwrap_or(false);
 
                 let blocks = if has_tool_calls {
-                    let tool_calls = c.message.tool_calls.as_ref().unwrap();
+                    let tool_calls = c.message.tool_calls.as_deref().unwrap_or_default();
                     tool_calls
                         .iter()
                         .map(|tc| {
@@ -199,7 +203,7 @@ impl LocalDriver {
                         .collect()
                 } else if has_content {
                     vec![ContentBlock::Text {
-                        text: c.message.content.clone().unwrap(),
+                        text: c.message.content.clone().unwrap_or_default(),
                     }]
                 } else {
                     vec![ContentBlock::Text {