docs: improve virtual environment setup instructions (#222)

Co-authored-by: Claude <noreply@anthropic.com>

CONTRIBUTING.md

@@ -27,7 +27,12 @@ project and how to get started as a developer.
 
    > **Note**: Basic Memory uses [just](https://just.systems) as a modern command runner. Install with `brew install just` or `cargo install just`.
 
-3. **Run the Tests**:
+3. **Activate the Virtual Environment**
+   ```bash
+   source .venv/bin/activate
+   ```
+
+4. **Run the Tests**:
    ```bash
    # Run all tests
    just test

justfile

@@ -3,6 +3,9 @@
 # Install dependencies
 install:
     pip install -e ".[dev]"
+    uv sync
+    @echo ""
+    @echo "💡 Remember to activate the virtual environment by running: source .venv/bin/activate"
 
 # Run unit tests in parallel
 test-unit: