refactor: move model definitions into providers and extract resolve module

- Rename ImageProvider to BlackForestProvider, TextProvider to MistralProvider
- Add get_provided_models() abstract method to Provider base class
- Move model lists from models.py into each provider's get_provided_models()
- Add providers/registry.py to aggregate models from all providers
- Extract infer_required_capabilities and resolve_model from config.py to resolve.py
- Update tests to use new names and import paths

bulkgen/cli.py

@@ -13,7 +13,7 @@ import typer
 from bulkgen.builder import BuildEvent, BuildResult, run_build
 from bulkgen.config import ProjectConfig, load_config
 from bulkgen.graph import build_graph, get_build_order
-from bulkgen.providers.models import ALL_MODELS
+from bulkgen.providers.registry import get_all_models
 
 app = typer.Typer(name="bulkgen", help="AI artifact build tool.")
 
@@ -182,9 +182,10 @@ def graph() -> None:
 @app.command()
 def models() -> None:
     """List available models and their capabilities."""
-    name_width = max(len(m.name) for m in ALL_MODELS)
-    provider_width = max(len(m.provider) for m in ALL_MODELS)
-    type_width = max(len(m.type) for m in ALL_MODELS)
+    all_models = get_all_models()
+    name_width = max(len(m.name) for m in all_models)
+    provider_width = max(len(m.provider) for m in all_models)
+    type_width = max(len(m.type) for m in all_models)
 
     header_name = "Model".ljust(name_width)
     header_provider = "Provider".ljust(provider_width)
@@ -210,7 +211,7 @@ def models() -> None:
         + "─" * len(header_caps)
     )
 
-    for model in ALL_MODELS:
+    for model in all_models:
         name_col = model.name.ljust(name_width)
         provider_col = model.provider.ljust(provider_width)
         type_col = model.type.ljust(type_width)