Replace hardcoded model aliases with dot-to-hyphen normalization

Instead of maintaining a brittle alias dict mapping model names to
dated API IDs, simply normalize dots to hyphens. The Anthropic API
accepts both claude-sonnet-4-5 and dated variants like
claude-sonnet-4-5-20250929, so no alias table is needed. This lets
users write "claude-sonnet-4.5" or "claude-sonnet-4-5" interchangeably.

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

nanobot/providers/anthropic_oauth.py

@@ -46,19 +46,14 @@ class AnthropicOAuthProvider(LLMProvider):
             return f"{self.api_base.rstrip('/')}/v1/messages"
         return self.ANTHROPIC_API_URL
 
-    # Short aliases that need dated suffixes for the API
-    MODEL_ALIASES: dict[str, str] = {
-        "claude-sonnet-4": "claude-sonnet-4-20250514",
-        "claude-opus-4": "claude-opus-4-20250514",
-        "claude-haiku-3-5": "claude-haiku-4-5-20241022",
-        "claude-sonnet-4-5": "claude-sonnet-4-5-20250929",
-        "claude-opus-4-5": "claude-opus-4-5-20250929",
-        "claude-opus-4-6": "claude-opus-4-6",
-    }
+    @staticmethod
+    def _normalize_model(model: str) -> str:
+        """Normalize model name for the Anthropic API.
 
-    def _resolve_model_alias(self, model: str) -> str:
-        """Resolve short model aliases to full dated IDs."""
-        return self.MODEL_ALIASES.get(model, model)
+        Anthropic model IDs use hyphens (claude-sonnet-4-5), but users often
+        write dots (claude-sonnet-4.5). Normalize so both work.
+        """
+        return model.replace(".", "-")
 
     async def _get_client(self) -> httpx.AsyncClient:
         """Get or create async HTTP client."""
@@ -253,8 +248,8 @@ class AnthropicOAuthProvider(LLMProvider):
         if "/" in model:
             model = model.split("/")[-1]
 
-        # Resolve short aliases to dated model IDs (API requires dated suffixes)
-        model = self._resolve_model_alias(model)
+        # Normalize dots to hyphens (claude-sonnet-4.5 -> claude-sonnet-4-5)
+        model = self._normalize_model(model)
 
         system, prepared_messages = self._prepare_messages(messages)
         anthropic_tools = self._convert_tools_to_anthropic(tools)