feat(llm-deepseek): support low reasoning effort

docs/config-catalog.md

@@ -859,7 +859,7 @@ export interface Config {
   /** Deployment thinking policy; `disabled` limits every conversation request to `off`. */
   thinking?: 'enabled' | 'disabled'
   /** Default thinking effort (default `high`); `off` disables thinking per request. */
-  reasoningEffort?: 'off' | 'high' | 'max'
+  reasoningEffort?: 'off' | 'low' | 'high' | 'max'
   /** Default per-request output cap (default 256,000); a model's own cap and explicit request values win. */
   maxTokens?: number
   /** Positive context capacity used when the selected model has no exact value (default 1,000,000). */