YNU-864: Add language harness skeleton

[ihsraham]

Summary

Adds the docs language harness skeleton without changing published documentation content.

What changed

• Added the root Vale config, including MDX-to-Markdown handling for Docusaurus docs.
• Added the Yellow Vale rule pack for AI-cadence wording, task-based labels, Build page shape, metaphor guardrails, spec voice, terse reference prose, and Learn/Protocol cross-link prompts.
• Added an advisory Vale pull-request workflow. It runs on docs, templates, and harness changes, reports error-level findings on added lines, and uses continue-on-error: true so it does not block merges yet.
• Added a local pre-commit hook entry that runs Vale on staged Markdown and MDX docs/templates when Vale is installed.
• Added starter templates for Learn pages, Build how-to pages, API Reference methods, Protocol pages, and Tutorials.

Why

This gives the docs repo a shared language and structure harness before the section-specific overlays and content follow-ups land. The first pass is intentionally advisory so existing docs content is not blocked by the new rules while teams adopt the templates and tune section-level enforcement.

Validation

• Parsed the workflow, pre-commit config, and Yellow rule YAML with Ruby YAML.
• Ran Vale 3.14.1 against the new templates: vale --minAlertLevel=error templates returned 0 findings.
• Ran git diff --check successfully.
• Ran npm run build successfully. The build still reports the existing Docusaurus deprecation, 0.5.x broken-link, and webpack warnings; this PR adds no docs pages or links.
• Verified the commit contains a 1Password SSH signature locally with an allowed-signers file.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 02ff4bf0-c57c-4c39-87b2-e5929fb7f2e3

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/ynu-864-language-harness-skeleton

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}