feat: add Mistral text generation provider

- Uses native async API (chat.complete_async)
- Appends text input file contents to prompt with headers
- Notes image inputs as attached references
- Writes raw LLM response directly to output file

bulkgen/providers/text.py

@@ -0,0 +1,63 @@
+"""Mistral text generation provider."""
+
+from __future__ import annotations
+
+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
+
+
+class TextProvider(Provider):
+    """Generates text via the Mistral API."""
+
+    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: str,
+        project_dir: Path,
+    ) -> None:
+        output_path = project_dir / target_name
+
+        content_parts: list[str] = [resolved_prompt]
+
+        for input_name in target_config.inputs:
+            input_path = project_dir / input_name
+            suffix = input_path.suffix.lower()
+
+            if suffix in IMAGE_EXTENSIONS:
+                content_parts.append(f"\n[Attached image: {input_name}]")
+            else:
+                file_content = input_path.read_text()
+                content_parts.append(
+                    f"\n--- Contents of {input_name} ---\n{file_content}"
+                )
+
+        full_prompt = "\n".join(content_parts)
+
+        async with Mistral(api_key=self._api_key) as client:
+            response = await client.chat.complete_async(
+                model=resolved_model,
+                messages=[models.UserMessage(content=full_prompt)],
+            )
+
+        if response is None or not response.choices:
+            msg = f"Mistral API returned no response 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)