[Mohamedajab]

The configuration guide uses FSSPEC_CONFIG_DIRECTORY in its precedence list, but the implementation reads FSSPEC_CONFIG_DIR. It also describes per-option environment values as strings, although valid JSON values are decoded.

Use the correct directory variable, explain that environment settings must be present before import, and add a short boolean-override example. No runtime behaviour changes.

Validation:

• All 8 configuration tests passed.
• Checked the example's boolean value and override order, and the directory setting in a fresh Python process.
• Pre-commit and git diff --check passed.
• Sphinx HTML build completed. It reported warnings in unchanged docstrings and an existing changelog entry; this was not a warning-free build.