fix(setup,chat): pass dummy api_key for local providers

litellm requires the api_key field even for local OpenAI-compatible
servers (LM Studio, llama.cpp). Use "local" as a sentinel value for
providers that don't require a real key.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pyra/chat/session.py

@@ -102,17 +102,17 @@ def _call_ai(cfg: PyraConfig, history: ConversationHistory) -> str:
     from pyra.vault.reader import get_key
 
     provider = get_provider(cfg.ai.provider_id)
-    api_key = get_key(cfg.ai.provider_id) if provider.requires_key else None
+    # Local providers don't need a real key but litellm requires the field
+    api_key = get_key(cfg.ai.provider_id) if provider.requires_key else "local"
 
     kwargs: dict = {
         "model": f"{provider.litellm_prefix}{cfg.ai.model}",
         "messages": history.build_for_api(),
         "stream": True,
+        "api_key": api_key,
     }
     if cfg.ai.base_url:
         kwargs["api_base"] = cfg.ai.base_url
-    if api_key:
-        kwargs["api_key"] = api_key
 
     litellm.suppress_debug_info = True
     stream = litellm.completion(**kwargs)