refactor: annotate remaining functions and arguments (#66)

[tschm]

Summary

Rhiza v1.2.2 adds flake8-annotations (ANN) to the ruff selection and runs mypy --strict. Both flag the same defect from two angles, which is why this was the highest-leverage item on the scorecard: one pass moves two gates.

Manual annotations

File	Change
core/server.py	get_response(scope), health_check, not_found_handler, server_error_handler
core/lifecycle.py	__enter__ -> "ChartServer", __exit__ + its three params
api/routes.py	get_data -> DataResponse
data/ingestion.py	`slice_opt(arr) -> list[Any]
demo.py	generate_ohlc -> tuple[...]

Plus ruff's own fixes

Ten -> None (and one -> str on root, which returns an HTML string) were applied via ruff check --select ANN --fix --unsafe-fixes — the same flags the pre-commit hook itself uses. Without these the ANN family isn't actually clean, so the issue's acceptance criterion needs them.

Two supporting decisions

• scope is typed MutableMapping[str, Any] — what starlette.types.Scope aliases to — rather than importing starlette. Starlette is a FastAPI transitive dep, not a declared one, so importing it directly would trip deptry.
• JSONResponse moved to the module imports so the handler return types can name it. This also removes two function-local re-imports of the same symbol.

The two unused handler args (ARG001) are deliberately left to #74, which owns them.

Verification

$ ruff@0.15.22 check --select ANN src demo.py
All checks passed!                     # v1.2.2 rule family, clean

$ mypy --strict src | grep -cE 'no-untyped-def|no-untyped-call'
0                                      # was 13
Found 43 errors  (was 55; remainder is #67/#68)

$ make fmt        -> all hooks Passed
$ make typecheck  -> ty: All checks passed!
$ make test       -> 154 passed, Total coverage: 100.00%

Note: master is on rhiza v0.18.8, whose ruff selection has no ANN and whose typecheck doesn't run mypy --strict. The v1.2.2 rule set was therefore run explicitly, pinned to the same ruff version the hook uses.

Closes #66

[Copilot]

Pull request overview

This PR completes a targeted pass of Python type annotations across the codebase to satisfy the newly-enabled Ruff ANN* rules and reduce mypy --strict “untyped def/call” findings, without changing runtime behavior.

Changes:

• Added missing argument and return type annotations in the FastAPI server (static file handler, endpoints, and exception handlers).
• Added missing -> None / context-manager method annotations in the server lifecycle controller, including __enter__ / __exit__ typing.
• Added/updated return types in the API route, data ingestion helper, and demo utilities.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/pycharting/data/ingestion.py	Adds explicit return type for DataManager.__init__ and types the slice_opt helper used for optional array slicing.
src/pycharting/core/server.py	Types ASGI scope for StaticFiles.get_response, adds endpoint/handler return types, and hoists JSONResponse import for typed handler returns.
src/pycharting/core/lifecycle.py	Adds missing -> None annotations on lifecycle helpers and fully types context manager methods (__enter__ / __exit__).
src/pycharting/api/routes.py	Annotates get_data to return the DataResponse model.
demo.py	Annotates demo helpers (generate_ohlc, run_demo, main) to satisfy annotation checks and clarify returned structures.

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