feat(llm): migrate from OpenRouter to OpusAgent

Replace OpenRouter (openai SDK) with OpusAgent REST API (httpx + polling).
LLMClient now creates topics per system prompt, submits async requests,
and polls for completion. Model tiers map to Claude model IDs
(opus-4-7, sonnet-4-6, haiku-4-5) configurable via env vars.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/run_pythagoras_smoke.py

@@ -410,16 +410,14 @@ def main() -> None:
     )
     loader = CerberoOHLCVLoader(client=cerbero, cache_dir=settings.series_dir)
 
-    # LLM client (qwen-2.5-72b tier C come da spec progetto - vedi MEMORY:
-    # cambiare modello senza ricalibrare = regressione dimostrata).
     llm = LLMClient(
-        openrouter_api_key=settings.openrouter_api_key.get_secret_value(),
+        opus_agent_api_key=settings.opus_agent_api_key.get_secret_value(),
+        opus_agent_base_url=settings.opus_agent_base_url,
         model_tier_s=settings.llm_model_tier_s,
         model_tier_a=settings.llm_model_tier_a,
         model_tier_b=settings.llm_model_tier_b,
         model_tier_c=settings.llm_model_tier_c,
         model_tier_d=settings.llm_model_tier_d,
-        openrouter_base_url=settings.openrouter_base_url,
     )
 
     # Setup DB winners (separato dal GA core DB).