docs: Use Claude to build out documentation.

I asked Claude to review all the code and build out documentation that
wolud be helpful to someone new to the Open edX ecosystem. This
documentation still needs further human review but saving it in a single
commit so that we can see what further changes were needed.

Author: feanil

CLAUDE.md

@@ -2,6 +2,37 @@
 
 This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
 
+## Project Purpose and Context
+
+This is a **sample plugin repository** that demonstrates all major Open edX plugin interfaces. It serves as a comprehensive example for developers new to Open edX plugin development.
+
+**Key Context:**
+- **Primary Goal**: Educational - show developers how to extend Open edX without modifying core platform code
+- **Plugin Types Demonstrated**: Django App Plugin, Events (signals), Filters, Frontend Slots, Tutor Plugin
+- **Real Business Logic**: Course archiving functionality (not just hello-world examples)
+- **Target Audience**: Developers new to Open edX plugin development
+
+**Repository Structure:**
+- `backend/` - Django app plugin with models, APIs, events, and filters
+- `frontend/` - React component for MFE slot customization  
+- `tutor/` - Tutor plugin for easy deployment
+- Each directory has comprehensive README.md files with TOCs
+
+**When Making Changes:**
+- Prioritize educational value and clear examples over production optimization
+- Always link to official Open edX documentation rather than duplicating it
+- Maintain working integration between all plugin types
+- Keep examples realistic but not overly complex
+
+**Key Files and Their Relationships:**
+- `backend/sample_plugin/apps.py` - Plugin registration and Django integration
+- `backend/sample_plugin/signals.py` - Open edX Events handlers
+- `backend/sample_plugin/pipeline.py` - Open edX Filters implementation
+- `backend/sample_plugin/models.py` - CourseArchiveStatus model (business logic)
+- `backend/sample_plugin/views.py` - REST API endpoints consumed by frontend
+- `frontend/src/plugin.jsx` - React component that replaces course list slot
+- `tutor/sample_plugin.py` - Deployment configuration (currently basic template)
+
 ## Build/Lint/Test Commands
 - Make sure to set the following so that test output is not too verbose: `export PYTEST_ADDOPTS="--disable-warnings --no-header --tb=short"`
 - Backend testing: `cd backend && pytest` or `cd backend && make test`
@@ -21,7 +52,23 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Always run `make quality` and fix issues before creating a PR to ensure consistent code style.
 
-## API Development Guidelines
-- Handle permission checking in viewsets rather than serializers to maintain separation of concerns
-- Use `perform_create()` and `perform_update()` in viewsets for business logic and permission validation
-- Test API endpoints for both regular user and admin/staff scenarios when permissions are involved
+## Code Modification Guidelines
+
+### Educational Constraints
+- **Primary Goal**: Preserve teaching value - don't optimize away clarity for performance
+- **Official Docs**: Always link to official Open edX documentation rather than duplicating explanations
+- **Integration Focus**: Ensure all plugin types continue to work together as demonstration
+- **Realistic Complexity**: Keep examples practical but not overly complex
+
+### Code Relationships to Preserve
+- **Backend ↔ Frontend**: CourseArchiveStatus API in `views.py` consumed by `frontend/src/plugin.jsx`
+- **Events ↔ Models**: Signal handlers in `signals.py` can update models in `models.py`
+- **Settings ↔ Filters**: Filter registration in `settings/common.py` must match classes in `pipeline.py`
+- **Apps.py ↔ All**: Plugin configuration affects URL routing, settings, and signal registration
+
+### Open edX Plugin Patterns
+- **API Development**: Use `perform_create()`/`perform_update()` in viewsets for business logic
+- **Settings**: Use additive approach for `OPEN_EDX_FILTERS_CONFIG` to avoid plugin conflicts
+- **Frontend**: Use Paragon components and `getAuthenticatedHttpClient()` for platform integration
+- **Events**: Import signal handlers in `apps.py ready()` method for proper registration
+- **Filters**: Return dictionaries with same parameter names as input, handle all scenarios