docs: add Claude Code infrastructure and skills

Add comprehensive Claude Code configuration for the Apify documentation repository:

- Main instructions.md with project overview, standards, and workflows
- Four specialized skills: doc-write, api-doc, tutorial, and review-docs
- Configuration file (claude.json) registering skills and context files
- User guide (README.md) with quick start and usage examples
- Setup summary documenting the complete infrastructure

All skills based on existing AGENTS.md and CONTRIBUTING.md standards to
ensure consistency across documentation. Includes templates, examples,
quality checklists, and best practices for common documentation tasks.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: marcel-rbro

.claude/README.md

@@ -0,0 +1,143 @@
+# Claude Code Configuration for Apify Docs
+
+This directory contains Claude Code configuration for the Apify documentation repository.
+
+## Structure
+
+```text
+.claude/
+├── README.md           # This file
+├── instructions.md     # Main instructions for Claude Code
+└── skills/             # Reusable skills for common tasks
+    ├── doc-write.md    # Documentation writing skill
+    ├── api-doc.md      # API documentation skill
+    ├── tutorial.md     # Tutorial creation skill
+    └── review-docs.md  # Documentation review skill
+```
+
+## How to Use
+
+### For Claude Code Users
+
+1. **Start a new session**: Claude Code will automatically read `instructions.md`
+2. **Use skills**: Type `/doc-write`, `/api-doc`, `/tutorial`, or `/review-docs` to use specific skills
+3. **Reference standards**: Always refer to `AGENTS.md` in the repo root for core standards
+
+### Available Skills
+
+#### `/doc-write` - Documentation Writing
+Create or edit documentation following Apify style guide.
+- Use for: New pages, content updates, reformatting
+- Handles: Style compliance, formatting, structure
+
+#### `/api-doc` - API Documentation
+Work with OpenAPI specifications and API endpoints.
+- Use for: New endpoints, schema updates, code samples
+- Handles: OpenAPI structure, operation IDs, examples
+
+#### `/tutorial` - Tutorial Creation
+Build structured, educational tutorials.
+- Use for: New tutorials, tutorial restructuring
+- Handles: Learning progression, examples, exercises
+
+#### `/review-docs` - Documentation Review
+Review documentation for quality and compliance.
+- Use for: Pre-submission checks, audits, consistency
+- Handles: Style guide compliance, accessibility, SEO
+
+## Quick Start
+
+### Writing New Documentation
+```
+Use /doc-write skill to create a new documentation page about [topic]
+```
+
+### Creating a Tutorial
+```
+Use /tutorial skill to create a tutorial on [topic]
+```
+
+### Adding API Endpoint
+```
+Use /api-doc skill to document the new [endpoint-name] endpoint
+```
+
+### Reviewing Documentation
+```
+Use /review-docs skill to review sources/platform/[file-name].md
+```
+
+## Primary References
+
+Always reference these files from the repo root:
+
+1. **`AGENTS.md`** - Core documentation standards (READ FIRST)
+2. **`CONTRIBUTING.md`** - Setup, workflows, style guide
+3. **`.cursor/rules/*.mdc`** - Cursor-specific rules (reference only)
+
+## Key Standards
+
+### Writing Style
+- US English, active voice, inclusive language
+- Sentence case for headings (not Title Case)
+- Action-oriented phrasing
+- No directional language (left/right)
+
+### Front Matter
+Every file needs:
+```yaml
+---
+title: "Action-oriented title"
+description: "140-160 chars, no 'documentation' word"
+sidebar_position: 1
+slug: /path/to/page
+---
+```
+
+### Formatting
+- **Bold** for UI elements
+- _Italics_ for emphasis
+- `code` for inline code/files
+- Code blocks with language tags
+- Admonitions for important info
+
+### Links & Images
+- Descriptive link text (not "click here")
+- Alt text for all images
+- Light theme for screenshots
+- Red indicators for highlighting
+
+## Testing
+
+Before submitting:
+```bash
+npm run lint:md      # Check markdown
+npm run lint:code    # Check code
+npm start            # Preview changes
+npm test             # Validate API specs
+```
+
+## Best Practices
+
+1. **Read `AGENTS.md` first** - It's the source of truth
+2. **Use the appropriate skill** - They're designed for specific tasks
+3. **Test code examples** - All examples must work
+4. **Check front matter** - Required for all files
+5. **Run linters** - Before committing
+6. **Review before submit** - Use `/review-docs`
+
+## Maintenance
+
+This configuration mirrors and extends the existing style guide:
+- `AGENTS.md` - Vendor-agnostic standards
+- `CONTRIBUTING.md` - Contribution process
+- `.cursor/rules/*.mdc` - Cursor-specific rules
+
+Keep these files in sync when updating documentation standards.
+
+## Need Help?
+
+- Questions about style: Check `AGENTS.md`
+- Setup issues: See `CONTRIBUTING.md`
+- Skill usage: Read the specific skill file
+- Claude Code general: Visit [Claude Code docs](https://github.com/anthropics/claude-code)