docs: note virtual environment requirement for pre-commit hooks (#745)

Some hooks require tools from dev dependency groups to be on PATH.
Add note to installation steps and common issues table directing
contributors to activate the virtual environment before committing.

Relates to #744.

Signed-off-by: Alex Bozarth <ajbozart@us.ibm.com>

Author: ajbozarth

CONTRIBUTING.md

@@ -71,6 +71,10 @@ to melleaadmin@ibm.com.
    ```bash
    pre-commit install
    ```
+   > **Note:** Some hooks require tools in dev dependency groups to be on your PATH. Activate the virtual environment before committing to ensure they are available:
+   > ```bash
+   > source .venv/bin/activate
+   > ```
 
 ### Installation with `conda`/`mamba`
 
@@ -430,7 +434,7 @@ CICD=1 uv run pytest
 | Output is wrong/None | Model too small or needs better prompt. Try larger model or add `reasoning` field. |
 | `error: can't find Rust compiler` | Python 3.13+ requires Rust for outlines. Install [Rust](https://www.rust-lang.org/tools/install) or use Python 3.12. |
 | Tests fail on Intel Mac | Use conda: `conda install 'torchvision>=0.22.0'` then `uv pip install mellea`. |
-| Pre-commit hooks fail | Run `pre-commit run --all-files` to see specific issues. Fix or use `git commit -n` to bypass. |
+| Pre-commit hooks fail | Run `pre-commit run --all-files` to see specific issues. Fix or use `git commit -n` to bypass. If a tool reports `command not found`, activate the virtual environment before committing: `source .venv/bin/activate`. |
 
 ### Debugging Tips