feat(model-info): ✨ add provider priority system and enhanced model metadata

This commit significantly improves the model lookup and metadata capabilities of the ModelInfoService:

- Introduces a provider priority system that prefers native/authoritative providers (anthropic, openai, google) over proxy/aggregator providers (openrouter, azure, requesty) when multiple sources exist for the same model
- Adds provider alias mapping to support custom provider names (e.g., nvidia_nim -> nvidia, gemini_cli -> google) for direct model ID resolution
- Extends ModelMetadata with new ModelInfo dataclass containing family, description, knowledge_cutoff, release_date, open_weights, status, tokenizer, and huggingface_id fields
- Adds extended capabilities support: structured_output, temperature, attachments, and interleaved content
- Implements version pattern normalization to handle different version formats (e.g., claude-opus-4-5 matches claude-opus-4.5)
- Refactors data merger to use best-source selection instead of averaging multiple sources, preserving queried model identity while inheriting technical specs from best matching native provider
- Restructures API response format with clear separation between core OpenAI fields, extended fields, legacy compatibility fields, and debug metadata
- Adds parent model tracking in origin field for transparency when fuzzy matching occurs
- Exports ModelMetadata in __all__ for public API access

The provider priority system ensures that when looking up custom provider models (e.g., antigravity/claude-opus-4-5), the service intelligently inherits accurate pricing and capabilities from the native provider source (anthropic/claude-opus-4.5) while preserving the queried model's provider identity.

Author: Mirrowel

src/rotator_library/__init__.py

@@ -7,19 +7,33 @@
 if TYPE_CHECKING:
     from .providers import PROVIDER_PLUGINS
     from .providers.provider_interface import ProviderInterface
-    from .model_info_service import ModelInfoService, ModelInfo
+    from .model_info_service import ModelInfoService, ModelInfo, ModelMetadata
+
+__all__ = [
+    "RotatingClient",
+    "PROVIDER_PLUGINS",
+    "ModelInfoService",
+    "ModelInfo",
+    "ModelMetadata",
+]
 
-__all__ = ["RotatingClient", "PROVIDER_PLUGINS", "ModelInfoService", "ModelInfo"]
 
 def __getattr__(name):
     """Lazy-load PROVIDER_PLUGINS and ModelInfoService to speed up module import."""
     if name == "PROVIDER_PLUGINS":
         from .providers import PROVIDER_PLUGINS
+
         return PROVIDER_PLUGINS
     if name == "ModelInfoService":
         from .model_info_service import ModelInfoService
+
         return ModelInfoService
     if name == "ModelInfo":
         from .model_info_service import ModelInfo
+
         return ModelInfo
+    if name == "ModelMetadata":
+        from .model_info_service import ModelMetadata
+
+        return ModelMetadata
     raise AttributeError(f"module {__name__!r} has no attribute {name!r}")