fix(py): type-check tests and examples; enforce the formatter

[schloerke]

Follow-up to #305, which turned up four gaps in the Python tooling. Closing them surfaced two annotations that were unusable from user code — which is the argument for closing them. One is ours; one is upstream.

Ours: page_react_html() was not accepted by App(ui=)

It declared HTMLTextDocument, but App(ui=) accepts only py-shiny's PageHtmlDocument subclass. shiny.App(page_react_html(...), server) — a documented path — failed to type-check while working fine at runtime. The class is imported from shiny.ui._page because py-shiny exports page_html() but not its return class.

Pinned by pkg-py/tests/test_typing.py, which asserts nothing at runtime — pyright failing is the test, the only thing that can catch an over-narrow annotation.

Upstream: Jsonifiable rejects the dict every app returns → posit-dev/py-shiny#2497

Jsonifiable spells its container arms as List and Dict. Both are invariant in their element types, so a render function returning dict[str, int] is not assignable to it, even though every element is itself Jsonifiable:

error: Argument of type "() -> dict[str, int]" cannot be assigned to parameter "_fn"
  of type "(() -> Jsonifiable) | (() -> Awaitable[Jsonifiable]) | None"

The single most ordinary thing a reactive_output does was a type error in five example apps.

I first fixed this locally with a covariant Mapping/Sequence alias, then reverted that in favor of filing posit-dev/py-shiny#2497, with a reproducer that uses only py-shiny's documented custom-renderer extension point — no shinyreact involved. A local alias would have fixed our five call sites and left the same trap for everyone else writing a Renderer[Jsonifiable].

So each site carries a suppression naming the issue instead:

# py-shiny#2497: `Jsonifiable`'s `dict`/`list` arms are invariant, so a
# `dict` return is not assignable to it. Drop the ignore when that lands.
@reactive_output  # pyright: ignore[reportArgumentType]
def dist_data():
    return histogram(waiting, input.bins())

grep 2497 finds all seven when it lands. Runtime behavior is unaffected — it is an annotation bug only.

The four tooling gaps

	Gap	Fix
1	py-check-format ran ruff check only, never ruff format --check — the formatter's output was unenforced, and test_output_error.py had already drifted	added ruff format --check; reformatted the drifted file
2	Both ruff targets scoped to pkg-py, leaving examples/ unlinted and unformatted — despite being shipped, read as documentation, and run by the default pytest invocation	both now cover $(PATHS_PY) = pkg-py examples
3	[tool.pyright] include was only pkg-py/src/shinyreact, so no test or example was type-checked	added pkg-py/tests and examples, and fixed the 50 pre-existing errors
4	tests-e2e asked for a shiny[playwright] extra py-shiny does not have (theme, otel, test, dev, doc, add-test) — uv reports this as a warning, not an error, on every sync	dropped the extra; pytest-playwright already pulls in playwright

The pre-existing errors, fixed in place

• test_input_handler.py / test_dep_discovery.py — NO_NAME / NO_SESSION / ANY_NAME casts, because these tests deliberately pass None for arguments the handlers ignore, which is part of what they assert.
• test_dep.py — dep_source() / first_script() / first_stylesheet() helpers. HTMLDependency normalizes these attributes in __init__ but keeps them declared as the wider argument types; narrowing once lets the assertions read as assertions instead of type gymnastics.
• test_bookmark_restore.py — local _config_html() helper takes Mapping, same invariance root cause as #2497.
• test_set_react_page.py — RenderedHTML, the TypedDict render() actually returns.
• 04-shadcn/app.py — .loc[:, [...]] instead of [[...]]; pandas types the latter as Series | Unknown, and Series.to_dict() takes no orient=.

Verification

• make py-check — ruff lint + format clean, pyright 0 errors over package + tests + examples, 198 passed
• make py-test-e2e (chromium) — 28 passed
• uv sync --all-extras --all-groups — no extras warning
• FEATURES.md updated for both the page_react_html return type and the #2497 suppression