fix: remove default for strix_llm, keep it required

strix/config/config.py

@@ -8,7 +8,7 @@ class Config:
     """Configuration Manager for Strix."""
 
     # LLM Configuration
-    strix_llm = "openai/gpt-5"
+    strix_llm = None
     llm_api_key = None
     llm_api_base = None
     openai_api_base = None

strix/interface/main.py

@@ -539,7 +539,7 @@ def main() -> None:
     is_whitebox = bool(args.local_sources)
 
     posthog.start(
-        model=os.getenv("STRIX_LLM"),
+        model=Config.get("strix_llm"),
         scan_mode=args.scan_mode,
         is_whitebox=is_whitebox,
         interactive=not args.non_interactive,