ruff 0.16 `format` rewrites Markdown — CI will auto-commit .md reformats fleet-wide

[thorwhalen]

Summary

ruff 0.16's format subcommand now formats Markdown files (it reformats Python code fences inside .md), not just .py. Because the wads CI format step runs in-place and pushes results back to the default branch, any repo with Python fences in its markdown will get auto-committed markdown reformats nobody asked for on its next default-branch merge.

Observed

In i2mint/ij, uvx ruff format . rewrote:

• PHASE2.md, PHASE3.md, PHASE4.md
• misc/REASEARCH.md

These were pre-existing drift (confirmed by running the same command against the untouched default branch), so the reformats were reverted out of the PR diff — but they will land the moment that branch merges and CI's format step runs.

Why it matters fleet-wide

• The wads CI format step is not --check; it rewrites and commits.
• Docs, READMEs and design notes with python fences are common across the fleet.
• The resulting commits are noise in the history and can conflict with in-flight branches (the rollout already requires a pull-before-push dance because of the version-bump + format push-back).

Decision needed

Pick one fleet-wide policy:

1. Exclude markdown from ruff formatting — add *.md to the ecosystem-standard [tool.ruff] exclude block that wads generates, and backfill it into existing repos.
2. Accept the churn — but then deliberately run a one-time ruff format pass per repo so the reformat lands in a reviewed commit rather than as a surprise CI push-back.

Option 1 is probably right: markdown formatting is a cosmetic concern that should not be coupled to the test/publish pipeline.

Note on ruff pinning

wads actions pin ruff==0.16.0 for uv-stub repos, but uv-inline repos invoke uvx ruff (latest), so inline repos will pick this behaviour up unpredictably as ruff releases.

Surfaced during the 2026-07-30 wave-0 rollout batch. Cross-ref: #51.