docs(recheck): document the recheck command and update the agent skills

[adamaltman]

What/Why/How?

The recheck command merged in #3080 with two short docs pages, and the engine's original documentation (the monorepo README) never came with it. This PR documents the command in full and brings the two recheck agent skills up to date with the redocly.yaml configuration.

Docs

• New "Markdown linting" sidebar group under docs/@v2/recheck/: overview and quickstart, presets, every Markdown rule with its options, prose assertions and scopes, Markdoc parsing and schema generation, and ways to suppress findings (file targeting, line exceptions, inline directives, baseline).
• Rewritten commands/recheck.md with every action, format, and exit code, and an expanded configuration/reference/recheck.md that explains how presets and the block merge.
• New guide: migrate from markdownlint and Vale.
• Links from the docs landing page, the guides index, and the configuration overview; recheck moved to its alphabetical place in the commands sidebar.

Skills

• recheck-lint and recheck-config updated for presets in the root extends and rules under recheck.rules, the severity-string versus rule-object distinction, the assertion merge edge, check-config, and the .redocly.recheck-baseline.yaml pickup.
• The skills stay in packages/recheck/skills/ (shipped in the package) and are also copied to .claude/skills/ next to the other skills, which is where the website publishes them from. The website still needs remote entries for the two new skills.
• The redocly-cli skill gets a recheck row and section.

Everything is checked against the engine source in this repo, not the monorepo README. Two features of the monorepo engine are not in the CLI yet and are left out of the docs: the word-count, sentence-count, and reading-time metric formulas (Redocly/redocly#28017).

Reference

Follows #3080.

Testing

• markdownlint-cli2 with .markdownlint.yaml on every changed Markdown file: clean.
• markdown-link-check with .markdown-link-check.json: no broken links; every intra-doc anchor verified with a script.
• oxfmt --check: clean.
• Vale rules checked by hand (no future tense, no gerund-first headings, US spelling, inclusive terms only inside code spans).
• redocly recheck run on the new pages with recheck/markdown, recheck/prose, and recheck/markdoc: the only findings are repo conventions that .markdownlint.yaml also turns off, plus two engine false positives tracked separately.

Check yourself

• This PR follows the contributing guide
• All new/updated code is covered by tests
• Core code changed? - Tested with other Redocly products (internal contributions only)
• New package installed? - Tested in different environments (browser/node)
• Documentation update has been considered

Security

• The security impact of the change has been considered
• Code follows company security practices and guidelines

🤖 Generated with Claude Code

---

Note

Low Risk
Documentation and agent skill content only; no runtime or CLI code changes in the diff.

Overview
Adds full Markdown and prose linting documentation for redocly recheck: a new docs/@v2/recheck/ section (overview, presets, Markdown rules, prose assertions, Markdoc, suppression/baseline), a substantially expanded commands/recheck.md (options, formats, exit codes, CI examples), and richer configuration/reference/recheck.md plus configuration overview links. A new migrate from markdownlint and Vale guide and sidebar/landing-page wiring surface the feature alongside API docs.

Agent skills are introduced or refreshed: recheck-lint and recheck-config in .claude/skills/ and packages/recheck/skills/, with redocly-cli, README, and changeset notes describing install via npx skills add. No engine or CLI behavior changes in this diff—docs and assistant guidance only.

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[changeset-bot]

⚠️ No Changeset found

Latest commit: 6fba241

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes changesets to release 6 packages

Name	Type
@redocly/cli	Minor
@redocly/openapi-core	Minor
@redocly/recheck	Minor
@redocly/client-generator	Patch
@redocly/respect-core	Minor
@redocly/reunite-integration	Minor

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	83.46% (🎯 79%)	20136 / 24125
🔵	Statements	83.09% (🎯 78%)	21758 / 26185
🔵	Functions	85.24% (🎯 82%)	3830 / 4493
🔵	Branches	75.61% (🎯 71%)	14626 / 19344

File Coverage

No changed files found.

Generated in workflow #12253 for commit 6fba241 by the Vitest Coverage Report Action

[github-actions]

Performance Benchmark (Lower is Faster)

CLI Version	Bundle	Lint	Check Config
cli-latest	▓ 1.01x ± 0.01	▓ 1.00x ± 0.01	▓ 1.00x ± 0.01
cli-next	▓ 1.00x (Fastest)	▓ 1.00x (Fastest)	▓ 1.00x (Fastest)