refactor: switch to basedpyright, remove pydantic-settings

- Replace pyright with basedpyright in devenv.nix (custom hook)
- Add basedpyright to devenv packages
- Fix all basedpyright warnings: add DiGraph[str] type args, annotate
  class attributes, narrow SyncResponse, handle unused call results,
  suppress unavoidable Any from yaml.safe_load and untyped blackforest
- Replace pydantic-settings[yaml] with direct pyyaml dependency
- Update CLAUDE.md to reflect basedpyright and dependency changes

bulkgen/providers/image.py

@@ -8,8 +8,13 @@ from pathlib import Path
 from typing import override
 
 import httpx
-from blackforest import BFLClient
-from blackforest.types.general.client_config import ClientConfig
+from blackforest import BFLClient  # pyright: ignore[reportMissingTypeStubs]
+from blackforest.types.general.client_config import (  # pyright: ignore[reportMissingTypeStubs]
+    ClientConfig,
+)
+from blackforest.types.responses.responses import (  # pyright: ignore[reportMissingTypeStubs]
+    SyncResponse,
+)
 
 from bulkgen.config import TargetConfig
 from bulkgen.providers import Provider
@@ -25,6 +30,8 @@ def _encode_image_b64(path: Path) -> str:
 class ImageProvider(Provider):
     """Generates images via the BlackForestLabs API."""
 
+    _client: BFLClient
+
     def __init__(self, api_key: str) -> None:
         self._client = BFLClient(api_key=api_key)
 
@@ -58,13 +65,20 @@ class ImageProvider(Provider):
             self._client.generate, resolved_model, inputs, _BFL_SYNC_CONFIG
         )
 
-        image_url: str | None = result.result.get("sample")  # type: ignore[union-attr]
+        if not isinstance(result, SyncResponse):
+            msg = (
+                f"BFL API returned unexpected response type for target '{target_name}'"
+            )
+            raise RuntimeError(msg)
+
+        result_dict: dict[str, str] = result.result  # pyright: ignore[reportUnknownMemberType, reportUnknownVariableType]
+        image_url = result_dict.get("sample")
         if not image_url:
             msg = f"BFL API did not return an image URL for target '{target_name}'"
             raise RuntimeError(msg)
 
         async with httpx.AsyncClient() as http:
             response = await http.get(image_url)
-            response.raise_for_status()
+            _ = response.raise_for_status()
 
-        output_path.write_bytes(response.content)
+        _ = output_path.write_bytes(response.content)