Add automated documentation validation workflow

[josbeir]

Implements GitHub Actions workflow to validate documentation PRs with four independent checks:

Checks:

• JS Syntax: Validates config.js syntax
• JSON Validation: Validates toc_*.json files
• Markdown Linting: Enforces VitePress-compatible rules (allows code groups, callouts, inline HTML)
• Spell Checking: Multi-language support (EN/JA) with technical term dictionary

Configuration:

• cspell.json: Lenient spellcheck config that ignores code blocks, PascalCase, snake_case, variables, URLs, and common PHP/CakePHP terms
• markdownlint.json: VitePress-optimized rules supporting Japanese characters and custom markdown features

Triggers on changes to docs/**, .github/**, toc_*.json, or config.js.

Notes about markdownlint.

The markdownlint config is pretty loose for now. Its kind of a baseline from which we can work our way up in future pr's :-)

[Copilot]

Pull request overview

This PR adds a comprehensive automated documentation validation workflow to enforce quality standards on documentation changes. The workflow includes four parallel validation checks: JavaScript syntax validation for config.js, JSON validation for table-of-contents files, Markdown linting with VitePress-compatible rules, and spell checking with multi-language support.

Changes:

• Adds GitHub Actions workflow with 4 independent validation jobs (JS, JSON, Markdown, Spelling)
• Configures markdownlint with VitePress-optimized rules supporting Japanese characters and custom HTML
• Configures cspell for multi-language spell checking with technical term dictionary and pattern ignoring

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 8 comments.

File	Description
.github/workflows/docs-validation.yml	Defines the validation workflow with 4 jobs for syntax checking, linting, and spell checking
.github/markdownlint.json	Configures markdown linting rules optimized for VitePress documentation
.github/cspell.json	Configures spell checker with technical terms, ignore patterns, and multi-language support

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.