**docs: remove outdated statistics-related documentation and add standards**

- **Removed Files**:
  - Deleted outdated statistics documentation files (`statistics.md`, `statistics-flush-solution.md`, `statistics-summary.md`) to clean up the repository and avoid confusion.

- **Added Standards**:
  - Introduced `DOCUMENTATION_STANDARDS.md` to outline naming conventions and troubleshooting practices for more consistent and maintainable project documentation.

- **Tests**:
  - Added a new test file `edge-cases.test.ts` to verify handling of edge cases, ensuring robust behavior against boundary values and invalid inputs.

**Purpose**: Cleans up deprecated documentation while introducing concrete standards for maintaining and updating documentation. Enhances test coverage for unusual or boundary inputs, improving overall system resilience.

tests/test-matrix.md

@@ -0,0 +1,127 @@
+# Brainy Test Matrix
+
+This document outlines a comprehensive testing strategy for the Brainy vector database, ensuring all functionality works correctly across different environments and configurations.
+
+## Test Dimensions
+
+The test matrix covers the following dimensions:
+
+1. **Public Methods**: All public methods of the BrainyData class
+2. **Storage Adapters**: All supported storage types
+3. **Environments**: All supported runtime environments
+4. **Test Types**: Happy path, error handling, edge cases, performance
+
+## Storage Adapters
+
+- Memory Storage
+- File System Storage
+- OPFS (Origin Private File System) Storage
+- S3-Compatible Storage (including R2)
+
+## Environments
+
+- Node.js
+- Browser
+- Web Worker
+- Worker Threads
+
+## Test Types
+
+- **Happy Path**: Tests with valid inputs and expected behavior
+- **Error Handling**: Tests with invalid inputs, error conditions
+- **Edge Cases**: Tests with boundary values, empty inputs, etc.
+- **Performance**: Tests measuring execution time with various dataset sizes
+
+## Core Method Test Matrix
+
+| Method | Memory | FileSystem | OPFS | S3 | Error Handling | Edge Cases | Performance |
+|--------|--------|------------|------|----|--------------------|------------|-------------|
+| init() | ✅ | ✅ | ⚠️ | ⚠️ | ⚠️ | ⚠️ | ❌ |
+| add() | ✅ | ✅ | ⚠️ | ❌ | ⚠️ | ⚠️ | ❌ |
+| addBatch() | ✅ | ✅ | ❌ | ❌ | ⚠️ | ❌ | ❌ |
+| search() | ✅ | ✅ | ⚠️ | ❌ | ⚠️ | ⚠️ | ❌ |
+| searchText() | ✅ | ✅ | ❌ | ❌ | ⚠️ | ❌ | ❌ |
+| get() | ✅ | ✅ | ❌ | ❌ | ⚠️ | ❌ | ❌ |
+| delete() | ✅ | ✅ | ❌ | ❌ | ⚠️ | ❌ | ❌ |
+| updateMetadata() | ✅ | ✅ | ❌ | ❌ | ❌ | ❌ | ❌ |
+| relate() | ⚠️ | ⚠️ | ❌ | ❌ | ❌ | ❌ | ❌ |
+| findSimilar() | ⚠️ | ⚠️ | ❌ | ❌ | ❌ | ❌ | ❌ |
+| clear() | ✅ | ✅ | ⚠️ | ❌ | ❌ | ❌ | ❌ |
+| isReadOnly()/setReadOnly() | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ |
+| getStatistics() | ⚠️ | ⚠️ | ❌ | ❌ | ❌ | ❌ | ❌ |
+| backup()/restore() | ⚠️ | ⚠️ | ❌ | ❌ | ❌ | ❌ | ❌ |
+
+Legend:
+- ✅ Well tested
+- ⚠️ Partially tested
+- ❌ Not tested
+
+## Environment Test Matrix
+
+| Environment | Memory | FileSystem | OPFS | S3 |
+|-------------|--------|------------|------|-----|
+| Node.js | ✅ | ✅ | N/A | ⚠️ |
+| Browser | ⚠️ | N/A | ⚠️ | ❌ |
+| Web Worker | ❌ | N/A | ❌ | ❌ |
+| Worker Threads | ❌ | ⚠️ | N/A | ❌ |
+
+## Testing Gaps to Address
+
+1. **Error handling scenarios** for each method
+   - Invalid inputs
+   - Network failures
+   - Storage failures
+   - Concurrent operation conflicts
+
+2. **Edge cases**
+   - Empty queries
+   - Invalid IDs
+   - Maximum size datasets
+   - Zero-length vectors
+   - Dimension mismatches
+
+3. **Different storage adapters**
+   - Complete OPFS testing
+   - Complete S3 testing
+   - Test adapter switching/fallback
+
+4. **Multi-environment behavior**
+   - Browser-specific tests
+   - Web Worker tests
+   - Worker Threads tests
+
+5. **Read-only mode enforcement**
+   - Test all write operations in read-only mode
+
+6. **Relationship operations**
+   - Complete testing for relate()
+   - Complete testing for findSimilar()
+
+7. **Metadata handling**
+   - Test metadata in add/relate operations
+   - Test updateMetadata edge cases
+
+8. **Large dataset operations**
+   - Performance with 10k+ vectors
+   - Memory usage optimization
+
+9. **Concurrent operations**
+   - Thread safety
+   - Race condition handling
+
+10. **Statistics and monitoring**
+    - Accuracy of statistics
+    - Performance impact of statistics tracking
+
+## Implementation Plan
+
+1. Create error handling tests for core methods
+2. Create edge case tests for core methods
+3. Complete storage adapter tests for OPFS and S3
+4. Create environment-specific test suites
+5. Implement read-only mode tests
+6. Complete relationship operation tests
+7. Create metadata handling tests
+8. Implement performance tests with various dataset sizes
+9. Create concurrent operation tests
+10. Complete statistics and monitoring tests