chore: exclude Markdown from ruff format scope

[ttw225]

Root cause

ruff 0.16.0 (2026-07-23) ships a breaking change:

Ruff can now format Python code blocks in Markdown files and will do this by
default.

Our lint jobs declare ruff>=0.4 with no upper bound, so CI adopted 0.16.0 on
its own and .md files entered ruff format's scope for the first time.
wren-langchain CI has been red on main since 2026-07-24.

Bisect in sdk/wren-langchain — the file count alone shows it:

ruff	files scanned	result
≤ 0.15.0	38 (= exactly the .py count)	pass
0.16.0	40 (38 .py + 2 .md)	fail

All 38 .py files are clean under 0.16.0. The failure comes entirely from
Markdown.

Why exclude rather than reformat

• Formatting Markdown buys no correctness. ruff silently skips code blocks
  it cannot parse — a .md holding syntactically invalid Python still reports
  1 file already formatted and exits 0. The check is cosmetic only.
• Coverage is incoherent. docs/core/sdk/langchain.md and
  docs/core/sdk/pydantic.md share snippets with the SDK READMEs but sit under
  no ruff config, so the same example is enforced in one file and unmanaged in
  the other.
• It recurs. With no upper bound on ruff and docs in scope, any future
  release can turn CI red on documentation again.
• The docs are hand-formatted on purpose. These READMEs align inline
  comments across a column of API-to-description pairs. ruff has declined to
  preserve alignment (Formatter: Keep right-hanging comments aligned astral-sh/ruff#7684, open since 2023; formatter: add config option to preserve leading whitespace before inline comments astral-sh/ruff#23578
  closed unmerged) — a fair call for code, a poor fit for a hand-tuned doc table.

extend-exclude = ["*.md"] is the opt-out Astral documents for this.

What

Added to every package carrying a ruff config:

• sdk/wren-langchain — fixes the red CI
• sdk/wren-pydantic — latent; its CI has not run since before the release
• core/wren — passing, but its lint runs uvx ruff (always newest)
• core/wren-core-py — no-op while pinned at 0.13.1

No documentation content is changed.

Test plan

Each package's own CI commands under ruff 0.16.0, plus 0.15.0 to confirm the
setting is inert on older versions — all pass: wren-langchain 38 files,
wren-pydantic 34, core/wren 69 (src/), wren-core-py 3.

Pre-existing and untouched: core/wren-core-py has an I001 in
tests/test_cube.py on main, identical with and without this change.

---

Separately: pinning ruff would not help core/wren — its lint calls uvx ruff,
which resolves independently of the project's dev dependencies. Happy to open an
issue if worth pursuing.

Summary by CodeRabbit

• Chores
  • Updated code-quality tooling configuration to exclude Markdown files from automated Ruff processing.
  • Added documentation clarifying Markdown formatting behavior in newer Ruff versions.

[coderabbitai]

Walkthrough

Ruff configurations in four Python projects now exclude Markdown files and document Ruff’s Markdown formatting behavior.

Changes

Ruff Markdown exclusion

Layer / File(s)	Summary
Configure Markdown exclusion core/wren-core-py/pyproject.toml, core/wren/pyproject.toml, sdk/wren-langchain/pyproject.toml, sdk/wren-pydantic/pyproject.toml	Ruff configurations add *.md to extend-exclude; comments explain the Markdown formatting behavior and hand-formatted documentation.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested reviewers: paulchen79

Poem

A rabbit hops through docs so neat,
While Ruff skips Markdown at its feet.
Four configs softly close the gate,
Hand-formatted pages keep their state.
Hop, hop—formatting feels complete!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: excluding Markdown files from Ruff formatting scope.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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