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/providers/text.py

@@ -1,114 +0,0 @@
-"""Mistral text generation provider."""
-
-from __future__ import annotations
-
-import base64
-import mimetypes
-from pathlib import Path
-from typing import override
-
-from mistralai import Mistral, models
-
-from bulkgen.config import IMAGE_EXTENSIONS, TargetConfig
-from bulkgen.providers import Provider
-from bulkgen.providers.models import ModelInfo
-
-
-def _image_to_data_url(path: Path) -> str:
-    """Read an image file and return a ``data:`` URL with base64-encoded content."""
-    mime = mimetypes.guess_type(path.name)[0] or "image/png"
-    b64 = base64.b64encode(path.read_bytes()).decode("ascii")
-    return f"data:{mime};base64,{b64}"
-
-
-class TextProvider(Provider):
-    """Generates text via the Mistral API."""
-
-    _api_key: str
-
-    def __init__(self, api_key: str) -> None:
-        self._api_key = api_key
-
-    @override
-    async def generate(
-        self,
-        target_name: str,
-        target_config: TargetConfig,
-        resolved_prompt: str,
-        resolved_model: ModelInfo,
-        project_dir: Path,
-    ) -> None:
-        output_path = project_dir / target_name
-
-        all_input_names = list(target_config.inputs) + list(
-            target_config.reference_images
-        )
-
-        has_images = any(
-            (project_dir / name).suffix.lower() in IMAGE_EXTENSIONS
-            for name in all_input_names
-        )
-
-        if has_images:
-            message = _build_multimodal_message(
-                resolved_prompt, all_input_names, project_dir
-            )
-        else:
-            message = _build_text_message(resolved_prompt, all_input_names, project_dir)
-
-        async with Mistral(api_key=self._api_key) as client:
-            response = await client.chat.complete_async(
-                model=resolved_model.name,
-                messages=[message],
-            )
-
-        if not response.choices:
-            msg = f"Mistral API returned no choices for target '{target_name}'"
-            raise RuntimeError(msg)
-
-        content = response.choices[0].message.content
-        if content is None:
-            msg = f"Mistral API returned empty content for target '{target_name}'"
-            raise RuntimeError(msg)
-
-        text = content if isinstance(content, str) else str(content)
-        _ = output_path.write_text(text)
-
-
-def _build_text_message(
-    prompt: str,
-    input_names: list[str],
-    project_dir: Path,
-) -> models.UserMessage:
-    """Build a plain-text message (no images)."""
-    parts: list[str] = [prompt]
-    for name in input_names:
-        file_content = (project_dir / name).read_text()
-        parts.append(f"\n--- Contents of {name} ---\n{file_content}")
-    return models.UserMessage(content="\n".join(parts))
-
-
-def _build_multimodal_message(
-    prompt: str,
-    input_names: list[str],
-    project_dir: Path,
-) -> models.UserMessage:
-    """Build a multimodal message with text and image chunks."""
-    chunks: list[models.TextChunk | models.ImageURLChunk] = [
-        models.TextChunk(text=prompt),
-    ]
-
-    for name in input_names:
-        input_path = project_dir / name
-        suffix = input_path.suffix.lower()
-
-        if suffix in IMAGE_EXTENSIONS:
-            data_url = _image_to_data_url(input_path)
-            chunks.append(models.ImageURLChunk(image_url=models.ImageURL(url=data_url)))
-        else:
-            file_content = input_path.read_text()
-            chunks.append(
-                models.TextChunk(text=f"\n--- Contents of {name} ---\n{file_content}")
-            )
-
-    return models.UserMessage(content=chunks)  # pyright: ignore[reportArgumentType]