fix(llm): exclude OpenRouter Novita provider via extra_body (Qwen 2.x rotto)

OpenRouter ha cominciato a routare qwen/qwen-2.5-72b-instruct attraverso
Novita, che rifiuta /chat/completions con HTTP 400:
"model: qwen/qwen-2.5-72b-instruct does not support endpoint: completions".

Aggiunto LLMClient.DEFAULT_PROVIDER_IGNORE = ("Novita",) e flag opzionale
provider_ignore al constructor. Le request includono ora
extra_body={"provider": {"ignore": ["Novita"]}} per default.

Verificato manualmente: con ignore Novita, qwen-2.5-72b risponde
normalmente via altri provider (DeepInfra, Together, ecc).

Mantenuta backward compat: passando provider_ignore=() si disabilita
l'esclusione (utile per test o se in futuro Novita si sistema).

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

src/multi_swarm/llm/client.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
+from typing import Any
 
 import openai
 from openai import OpenAI
@@ -44,6 +45,10 @@ class CompletionResult:
 
 
 class LLMClient:
+    # Provider OpenRouter da escludere di default. Novita rifiuta /completions
+    # endpoint per modelli Qwen 2.x — vedi bug 2026-05-12.
+    DEFAULT_PROVIDER_IGNORE: tuple[str, ...] = ("Novita",)
+
     def __init__(
         self,
         openrouter_api_key: str,
@@ -53,6 +58,7 @@ class LLMClient:
         model_tier_c: str = MODEL_TIER_C,
         model_tier_d: str = MODEL_TIER_D,
         openrouter_base_url: str = OPENROUTER_BASE_URL,
+        provider_ignore: tuple[str, ...] | None = None,
     ) -> None:
         self.model_tier_s = model_tier_s
         self.model_tier_a = model_tier_a
@@ -60,6 +66,9 @@ class LLMClient:
         self.model_tier_c = model_tier_c
         self.model_tier_d = model_tier_d
         self.openrouter_base_url = openrouter_base_url
+        self._provider_ignore = (
+            provider_ignore if provider_ignore is not None else self.DEFAULT_PROVIDER_IGNORE
+        )
         self._tier_models: dict[ModelTier, str] = {
             ModelTier.S: model_tier_s,
             ModelTier.A: model_tier_a,
@@ -83,6 +92,9 @@ class LLMClient:
         max_tokens: int = 2000,
     ) -> CompletionResult:
         model = self._tier_models[genome.model_tier]
+        extra_body: dict[str, Any] = {}
+        if self._provider_ignore:
+            extra_body["provider"] = {"ignore": list(self._provider_ignore)}
         resp = self._client.chat.completions.create(
             model=model,
             messages=[
@@ -92,6 +104,7 @@ class LLMClient:
             temperature=genome.temperature,
             top_p=genome.top_p,
             max_tokens=max_tokens,
+            extra_body=extra_body or None,
         )
         if not resp.choices or resp.choices[0].message.content is None:
             raise EmptyCompletionError(f"empty response from {model}")