feat: configurable report language (default zh-CN)

Add providers.yaml `language` / Action input `language`; prompts and
published summary/inline honor it. Soften fail-closed messaging when
models 429; prefer cohere/nvidia in the first-3 parallel set for dogfood.

config/providers.yaml

@@ -1,6 +1,8 @@
 # Example / owner consumer override — OpenRouter only.
 # `key` is free-form; map it in the workflow step env from secrets.
 
+language: zh-CN
+
 agreement_min: 2
 temperature: 0
 max_tokens: 4096
@@ -10,7 +12,7 @@ providers:
     key: OPENROUTER_API_KEY
     protocol: openai
     models:
-      - google/gemma-4-31b-it:free
-      - google/gemma-4-26b-a4b-it:free
       - cohere/north-mini-code:free
       - nvidia/nemotron-3-nano-omni-30b-a3b-reasoning:free
+      - google/gemma-4-31b-it:free
+      - google/gemma-4-26b-a4b-it:free