docs: Add GitHib copilot instruction files (#2146)

<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Adds `.github/copilot-instructions.md` detailing repo-specific context
and writing guidelines for AI tools (OpenAPI pipeline, theme, patterns,
QA, and style).
> 
> - **Docs**:
> - **New AI agent guide** in `.github/copilot-instructions.md`
providing:
> - **Project overview & architecture**: Docusaurus multi-repo setup,
custom theme workspace.
> - **OpenAPI build pipeline**: source locations, Redocly plugins, build
command, generated outputs.
> - **Project patterns**: OpenAPI code samples, slug collection,
external link processing, LLMs.txt generation.
> - **Quality & pitfalls**: broken links, frontmatter, code block
languages; local build, linting, OpenAPI validation.
>     - **Quick reference** for common tasks and navigation updates.
> - **Writing & style guidelines**: frontmatter schema, naming,
formatting, admonitions, terminology.
> - **Content review checklist** and **doc type guidelines**; related
references (`CONTRIBUTING.md`, `AGENTS.md`).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
8c34a1b. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: marcel-rbro

.github/copilot-instructions.md

@@ -0,0 +1,200 @@
+# Apify Documentation - AI Agent Guide
+
+## Part 1: Repository-Specific Information
+
+### Project Overview
+
+Docusaurus-based documentation site combining:
+
+- **Platform docs** (`/sources/platform/`) - Product documentation
+- **Academy** (`/sources/academy/`) - Educational courses
+- **API reference** (`/apify-api/`) - Generated from OpenAPI specs
+- **Multi-repo architecture** - SDK/Client docs from separate repos served via nginx
+
+**Key insight:** ONE unified site built from MULTIPLE repositories. See CONTRIBUTING.md for multi-repo setup.
+
+### Architecture & Critical Workflows
+
+#### OpenAPI Documentation Build Pipeline
+
+**Critical:** API docs are generated, NOT hand-written. The workflow:
+
+1. **Source of truth**: `apify-api/openapi/openapi.yaml` (splits into `/paths` and `/components`)
+2. **Redocly plugins** (`apify-api/plugins/apify.mjs`) inject custom behavior:
+
+   - `code-samples-decorator.mjs` - Auto-adds code samples if files exist in `/code_samples/{js,curl}/`
+   - `legacy-doc-url-decorator.mjs` - Adds backward-compatible URLs
+   - `client-references-links-decorator.mjs` - Links to client library docs
+
+3. **Build command**: `npm run api:rebuild` = clean + bundle with Redocly + generate with Docusaurus
+4. **Output**: Markdown files in `apify-api/docs/` (gitignored, regenerated on each build)
+
+**Never edit generated files directly**. Edit the OpenAPI YAML or add code samples to trigger auto-inclusion.
+
+#### Custom Theme System
+
+Shared theme in `apify-docs-theme/` workspace:
+
+- Single source of truth for navigation, styling, components
+- Used across all 6+ documentation repos
+- Changes here propagate via CI to all projects
+- Key files: `src/config.js` (nav structure), `src/theme.js` (Docusaurus theme config)
+
+### Project-Specific Patterns
+
+#### OpenAPI Code Samples
+
+Add code samples by creating files in `apify-api/openapi/code_samples/{javascript,curl}/`:
+
+- Filename MUST match `operationId` from OpenAPI spec
+- Example: `actorRun_get.js` for operation with `operationId: "actorRun_get"`
+- Decorator auto-detects and adds `x-codeSamples` property
+- Missing samples logged during build (check console)
+
+#### Slug Collection Pattern
+
+`tools/utils/collectSlugs.js` recursively scans directories for `slug:` in frontmatter. Used in `docusaurus.config.js` to build dynamic navigation with `activeBaseRegex` patterns. When adding new sections, ensure slugs are collected for nav highlighting.
+
+#### External Link Processing
+
+`tools/utils/externalLink.js` rehype plugin auto-adds `target="_blank"` and `rel="noopener noreferrer"` to external links. Internal links (same domain) are detected via `isInternal()` helper.
+
+#### LLMs.txt Generation
+
+Post-build (`scripts/joinLlmsFiles.mjs` + `indentLlmsFile.mjs`):
+
+- Combines `llms.txt` from all sections into root
+- Used by AI tools for context (via `@signalwire/docusaurus-plugin-llms-txt`)
+- Edit source `llms.txt` files in content dirs, not the generated root one
+
+### Common Pitfalls
+
+1. **Editing generated API docs** - Always edit OpenAPI YAML source, never generated markdown
+2. **Broken links on build** - `onBrokenLinks: 'throw'` fails CI. Check slugs match file paths
+3. **Missing frontmatter** - Description or slug errors break SEO and navigation
+4. **Missing code block language** - Always specify language for syntax highlighting
+
+### Testing & Quality
+
+- **Local build test**: `npm run build` - Catches broken links, bad frontmatter
+- **Linting**: `npm run lint:fix` - Auto-fixes markdown + code style issues
+- **Link validation**: Docusaurus throws on broken internal links (see `onBrokenLinks` in config)
+- **OpenAPI validation**: `npm run redoc:test` - Validates OpenAPI spec with Redocly
+
+### Quick Reference
+
+- **Add new doc**: Create `.md` in `/sources/{platform,academy}/`, add frontmatter with title/description/slug
+- **Add API endpoint**: Edit `/apify-api/openapi/paths/**/*.yaml`, add code samples, run `npm run api:rebuild`
+- **Update navigation**: Edit `/sources/{platform,academy}/sidebars.js`
+- **Fix broken build**: Check `onBrokenLinks` errors, verify slugs match file paths, validate frontmatter
+
+## Part 2: Writing & Style Guidelines
+
+### Content Standards (Microsoft Style Guide Based)
+
+#### Frontmatter Requirements
+
+Every `.md`/`.mdx` file needs:
+
+```yaml
+---
+title: "Sentence case title (action-oriented)"
+description: "140-160 chars - explain value, not features"
+sidebar_position: 1
+slug: /path/to/page
+---
+```
+
+#### File Naming & Organization
+
+- **Kebab-case filenames**: `web-scraping-basics.md` (never camelCase or snake_case)
+- **Match slug to file path**: `/sources/platform/actors/running.md` → `slug: /platform/actors/running`
+
+#### Text Formatting Conventions
+
+- **Bold** for UI elements, buttons, tabs, menu items only: "Click **Save & Run**". Never use bold for emphasis.
+- *Italics* for emphasis (use sparingly)
+- `code` for inline code, file paths, API parameters: "Set `timeout` in `INPUT.json`"
+- Code blocks MUST specify language: ` ```javascript `, ` ```python `, ` ```bash `
+- Use [code tabs](https://docusaurus.io/docs/markdown-features/tabs) for multi-language examples
+
+#### Writing Style
+
+- Use simple English - prefer "use" over "utilize", favor simple sentence structures
+- Use American English spelling: "color" not "colour"
+- Use Oxford commas in lists
+- Use sentence case for headings and titles (not title case)
+- **Never make assumptions about product features** - ask if unsure
+
+#### Admonitions (Docusaurus-specific)
+
+**All admonitions must have a title.** Available types: `note`, `tip`, `info`, `caution`, `danger`
+
+```markdown
+:::note Important information
+
+Standard informational note.
+
+:::
+
+:::tip Pro tip
+
+Helpful advice for advanced users.
+
+:::
+
+:::caution Warning
+
+Something that could cause issues.
+
+:::
+```
+
+#### Terminology & Word List
+
+Use exact capitalization and phrasing:
+
+- **Apify Actor** (never "Apify actor")
+- **Apify Proxy**
+- **Apify Console** (never "the Apify Console")
+- **Apify Store** (never "the Apify Store")
+- **the Apify team**
+- **the Apify platform**
+- **AI agent**, **MCP server** (lowercase for generic terms)
+
+### Content Review Checklist
+
+When reviewing or creating documentation:
+
+- **Clarity**: Instructions are easy to understand
+- **Consistency**: Uniform terminology (see word list above) and style throughout
+- **Grammar & Spelling**: Correct errors, use American English
+- **Structure**: Logical flow, no duplicate content, appropriate headings/lists
+- **Links**: Verify all links are functional and relevant, link key terms to their docs
+- **Code snippets**: Developer-provided; check comments and obvious mistakes only
+
+### Documentation Type Guidelines
+
+**Platform documentation** (`sources/platform/**/*.md`):
+
+- Focus on practical, actionable guidance
+- Include real-world examples and use cases
+- Reference related API endpoints when applicable
+
+**Academy content** (`sources/academy/**/*.md`):
+
+- Structure content for learning progression
+- Include hands-on exercises and examples
+- Provide clear prerequisites and next steps
+
+**MDX files** (`sources/**/*.mdx`):
+
+- Use component imports and JSX syntax appropriately
+- Ensure proper frontmatter formatting
+- Test component rendering during development
+
+## Related Documentation
+
+- Full contribution guide: `CONTRIBUTING.md`
+- Style standards: `AGENTS.md` (vendor-agnostic rules)
+- Cursor-specific rules: `.cursor/rules/*.mdc` (if using Cursor)