**feat(docs): add compatibility and testing guides; enforce Universal Sentence Encoder usage**

- Added new documentation files:
  - `COMPATIBILITY.md` detailing environment-specific compatibility and behavior (Node.js, Browser, Worker).
  - `TESTING.md` providing instructions for verifying cache detection across environments.
  - Created browser (`test-browser-cache-detection.html`) and worker (`test-worker-cache-detection.html`) test scripts to validate cache mechanisms.

- Removed fallback mechanisms for embedding:
  - Updated `embedding.ts` to enforce strict usage of Universal Sentence Encoder (USE).
  - Fallback methods (`generateFallbackVector`) and related logic have been removed.
  - Errors are thrown when USE initialization or embedding fails, ensuring stricter reliability.

- Improved error handling:
  - Standardized error throwing for all USE-related failures across single and batch embeddings.
  - Logging updated to reflect critical embedding issues without allowing degraded operations.

**Purpose**: Improve documentation for environment compatibility and testing while enforcing consistent use of Universal Sentence Encoder for deterministic embeddings, removing unreliable fallback mechanisms.

TESTING.md

@@ -0,0 +1,97 @@
+# Testing Brainy Across Different Environments
+
+This document provides instructions for testing Brainy's cache detection functionality across different environments.
+
+## Testing in Node.js Environment
+
+To test Brainy in a Node.js environment:
+
+1. Build the project:
+   ```bash
+   npm run build
+   ```
+
+2. Run the Node.js test script:
+   ```bash
+   node test-cache-detection.js
+   ```
+
+3. Expected output:
+   ```
+   Brainy: Successfully patched TensorFlow.js PlatformNode at module load time
+   Applied TensorFlow.js patch via ES modules in setup.ts
+   Brainy running in Node.js environment
+   Creating BrainyData instance...
+   BrainyData instance created successfully!
+   Test completed successfully!
+   ```
+
+## Testing in Browser Environment
+
+To test Brainy in a browser environment:
+
+1. Build the project:
+   ```bash
+   npm run build
+   ```
+
+2. Start a local web server:
+   ```bash
+   npx http-server -p 8080
+   ```
+
+3. Open the browser test page:
+   ```
+   http://localhost:8080/test-browser-cache-detection.html
+   ```
+
+4. Click the "Run Test" button on the page.
+
+5. Expected results:
+   - The page should display success messages
+   - No errors should appear in the browser console
+   - You should see "BrainyData instance created successfully!" and "Test completed successfully!"
+
+## Testing in Web Worker Environment
+
+To test Brainy in a Web Worker environment:
+
+1. Build the project:
+   ```bash
+   npm run build
+   ```
+
+2. Start a local web server:
+   ```bash
+   npx http-server -p 8080
+   ```
+
+3. Open the worker test page:
+   ```
+   http://localhost:8080/test-worker-cache-detection.html
+   ```
+
+4. Click the "Run Test" button on the page.
+
+5. Expected results:
+   - The page should display success messages from the worker
+   - No errors should appear in the browser console
+   - You should see "BrainyData instance created successfully!" and "Test completed successfully!"
+
+## Compatibility Notes
+
+Brainy's cache detection has been designed to work across all environments:
+
+1. **Node.js Environment**:
+   - Uses fixed default memory values (8GB total, 4GB free) for cache size calculation
+   - This approach ensures compatibility with ES modules
+
+2. **Browser Environment**:
+   - Uses navigator.deviceMemory API when available
+   - Falls back to conservative defaults when the API is not available
+
+3. **Worker Environment**:
+   - Uses a more conservative approach to cache sizing
+   - Automatically detects the worker environment and adjusts accordingly
+
+The cache manager automatically detects the environment and adjusts its behavior to ensure optimal performance in each context.