fix: 模型思考模式配置 + Unicode 截断 + 审计修复 (13 files)

模型模式:
- 新增 LLMConfig/Source.ThinkingEnabled 配置，通过 ExtraBody
  控制 DeepSeek thinking mode，默认关闭
- SeedDefaults/ToConfig 读写 core.llm.thinking_enabled
- deepseek.lua 移除硬编码 temperature=0

Unicode 截断:
- truncateStr 改按 rune 计数，修复中文截断乱码

审计修复 (Critical):
- graph.go: defer rows.Close 在 for 循环 → 显式 Close (连接池泄漏)
- cli/openclaw/plugin.go: bare type assertion → comma-ok (panic)
- channel.go: payload["type"].(string) → comma-ok (panic)
- webui/handler.go: .(string) → fmt.Sprint (panic)
- agent.go: 添加 nil provider 错误返回

审计修复 (High):
- events/bus.go: copy handler slice under RLock (data race)
- webui/handler.go: SSE 通过 channel 串行化写入 (data race)
- timer/plugin.go: time.Sleep → select with stopCh (Stop 阻塞)
- provider.go: stream ch <- 添加 select ctx.Done (goroutine 泄漏)
- main.go: outputCh goroutine 添加 ctx.Done 退出路径

internal/agent/api/provider.go

@@ -265,13 +265,17 @@ func (p *OpenAIProvider) ChatStream(ctx context.Context, req *CompletionRequest)
 			}
 
 			if err := decoder.Decode(&line); err != nil {
-				break
+				return
 			}
 
 			if len(line.Choices) > 0 {
-				ch <- StreamChunk{
+				select {
+				case ch <- StreamChunk{
 					Content: line.Choices[0].Delta.Content,
 					Done:    line.Choices[0].FinishReason != nil,
+				}:
+				case <-ctx.Done():
+					return
 				}
 			}
 		}
@@ -498,9 +502,13 @@ func (p *LuaAdaptedProvider) ChatStream(ctx context.Context, req *CompletionRequ
 					continue
 				}
 				if len(raw.Choices) > 0 {
-					ch <- StreamChunk{
+					select {
+					case ch <- StreamChunk{
 						Content: raw.Choices[0].Delta.Content,
 						Done:    raw.Choices[0].FinishReason != nil,
+					}:
+					case <-ctx.Done():
+						return
 					}
 				}
 				continue
@@ -509,7 +517,11 @@ func (p *LuaAdaptedProvider) ChatStream(ctx context.Context, req *CompletionRequ
 			// Lua 返回了变换后的统一格式
 			var chunk StreamChunk
 			if err := json.Unmarshal([]byte(unified), &chunk); err == nil {
-				ch <- chunk
+				select {
+				case ch <- chunk:
+				case <-ctx.Done():
+					return
+				}
 			}
 		}
 	}()