docs: update CLAUDE.md with info about latest changes

Author: mkczarkowski

CLAUDE.md

@@ -107,4 +107,23 @@ Rules are defined as TypeScript objects and exported from category-specific file
 2. Use feature flags to control new functionality rollout across environments
 3. Collections allow users to save and share rule combinations with authentication
 4. The MCP server enables programmatic access for AI assistants (Cursor, Claude, etc.)
-5. Run `npm run generate-rules` after modifying rules to update `preparedRules.json` for MCP server
+5. Run `npm run generate-rules` after modifying rules to update `preparedRules.json` for MCP server
+
+## Important Development Instructions
+
+### Key Development Principles
+- Do what has been asked; nothing more, nothing less
+- NEVER create files unless they're absolutely necessary for achieving your goal
+- ALWAYS prefer editing existing files to creating new ones
+- NEVER proactively create documentation files (*.md) or README files unless explicitly requested
+
+### Working with Rules
+- When adding new rules, they must be added to both `src/data/rules/` TypeScript files AND corresponding translations in `src/i18n/translations.ts`
+- Unit tests will fail if translations are missing for new rules
+- Always run `npm run migrate-rules` after adding rules to sync them with the database
+- Run `npm run generate-rules` after modifying rules to update `preparedRules.json` for the MCP server
+
+### Database vs File-Based Rules
+- The system supports both database-stored rules (default) and file-based fallback
+- Use `USE_DATABASE_RULES=false` environment variable to force file-based rules during development
+- Database rules allow updates without code deployments