chore: hard-wrap markdown at 80 cols via prettier + pre-commit

[edochi]

Flips the repo's markdown convention from "no hard-wrap" to a hard 80-column wrap, enforced by prettier via a pre-commit hook and a CI check.

MD013 was firing on essentially every markdown file in editors. MD013 has no auto-fix, so the choice was to disable the rule or adopt wrapping; this PR adopts wrapping.

Tooling

File	Role
.prettierrc.yaml	proseWrap: always, printWidth: 80, embeddedLanguageFormatting: off
.prettierignore	fixtures, corpora, generated CHANGELOG.md, target/
.markdownlint-cli2.yaml	MD013 at 80 with code_blocks / tables / headings off
.pre-commit-config.yaml	local prettier@3.6.2 hook, language: node
Justfile	just fmt-md / just check-md
ci.yml	fmt-md job running prettier --check

Setup is uv tool install pre-commit && pre-commit install. uv tool, not uvx — pre-commit install bakes the interpreter path into .git/hooks/pre-commit, and a uvx cache entry can be pruned out from under it. Node and prettier are provisioned by pre-commit; nothing needs a global npm install.

Tables, fenced code blocks, headings and long URLs are deliberately left over-length. MD013 disables those three checks and is non-strict for lines with no space past the limit, so the two tools agree on what "formatted" means.

embeddedLanguageFormatting: off stops prettier rewriting the contents of fences whose language it can parse (json, yaml, js) — otherwise doc examples get silently reformatted.

Fixtures and corpora are excluded from both tools because their exact frontmatter bytes are under test: prettier rewrites YAML frontmatter (quote style, indentation, flow-sequence spacing) and doesn't recognise TOML +++ or bare-brace JSON frontmatter at all.

Verification

Every file was rendered before and after through CommonMark + GFM tables, with the HTML whitespace-normalised and compared. 276 files reformatted, zero unintended rendering changes. Prettier is idempotent across the repo, mdbook build passes, no fixture or non-markdown file was touched, and MD013 violations went from ~3,400 to 0.

Five files hand-fixed first

Two root causes, both of which silently change rendered output:

Bare snake_case identifiers pairing as emphasis across a code span. In TODO-0184, prettier turned write_index into write*index and ate the spaces around three adjacent code spans:

- **Pipeline-behavior** (classify, write_index decisions, search
  result count, error handling, `auto_*` chains) → switch

- **Pipeline-behavior** (classify, write*index decisions, search result count,
  error handling, `auto*\*`chains) → switch`EmbeddingModelConfig`to`provider:

TODO-0106 and TODO-0162 were worse: the first pass rewrote *every* to _every_, and that new underscore then paired with a bare one earlier in the paragraph on the second pass. Formatted, committed, clean — and corrupting on next touch. The pre-commit hook cannot detect this, because it only ever sees the file it just rewrote. This is what the CI job is for.

Unescaped pipes inside code spans in table cells. | `"value {value} {< | >} {limit}"` | was already splitting cells; after reformatting the whole table degraded to a paragraph of literal pipes. Fixed with \|.

TODO-0155 also moves from a tight to a loose list — prettier always inserts a blank line before a fence inside a list item, so the blank lines are now explicit rather than surfacing in some later unrelated diff.

Commits

• e5cf18b — configs, hook, AGENTS.md rule
• 8a15864 — just recipes, CI job, trimmed comments
• 46a3cb7 — the reformat (273 files)

The reformat is mechanical and kept in its own commit; review the first two and skim the third.

Note

Prettier 3.6.2 is pinned in three places (.pre-commit-config.yaml, Justfile, ci.yml). Bump all three together — the alternative is CI and local disagreeing about what "formatted" means.