feat: add ty type checker as prek hook

Add ty (Astral's Rust-based type checker) alongside existing linting:
- Add ty as dev dependency with error-on-warning config
- Add local-ty prek hook (language: unsupported, serial, full check)
- Fix type errors found by ty (api.py return type, unused type: ignore)

Author: albertotb

.pre-commit-config.yaml

@@ -49,3 +49,11 @@ repos:
     rev: 0.10.12
     hooks:
       - id: uv-lock
+  - repo: local
+    hooks:
+      - id: local-ty
+        name: ty check
+        entry: uv run ty check template tests
+        require_serial: true
+        language: unsupported
+        pass_filenames: false

pyproject.toml

@@ -74,10 +74,14 @@ xfail_strict = true
 addopts = ["-ra", "--strict-config", "--strict-markers"]
 filterwarnings = ["error", "ignore::DeprecationWarning"]
 
+[tool.ty.terminal]
+error-on-warning = true
+
 [dependency-groups]
 dev = [
     "pytest",
     "ruff",
     "prek",
     "ipykernel",
+    "ty",
 ]

template/api.py

@@ -43,7 +43,7 @@ def read_root() -> dict[str, str]:
 @app.post("/predict")
 def predict(request: Request) -> Response:
     """Mock prediction endpoint."""
-    return {"output": request.input}
+    return Response(output=request.input)
 
 
 if __name__ == "__main__":

template/main.py

@@ -4,7 +4,7 @@
 
 from importlib.metadata import PackageNotFoundError, version
 
-import typer  # type: ignore
+import typer
 
 try:
     __version__: str | None = version("template")