Summary

Update the api-key action input description to document its current fallback behavior.

Motivation

Since #665, enabling use-policy-store without an API key no longer fails the action. Harden-Runner emits a warning and defaults to audit mode, but action.yml still says the key is required.

Changes

• Document the audit-mode fallback in the api-key input description.
• Keep runtime behavior unchanged.

Validation

• git diff --check
• npm test -- --runInBand (67 tests passed)
• npm run build (passed; no dist/ changes)
• Parsed action.yml as YAML and checked the updated description
• npm run lint reports 80 existing errors in unchanged src/ files