Three docs pages updated:
- security.md: New 'Credential File Passthrough' section, updated
sandbox filter table to include Docker/Modal rows, added info box
about Docker env_passthrough merge
- creating-skills.md: New 'Credential File Requirements' section
with frontmatter examples and guidance on when to use env vars
vs credential files
- environment-variables.md: Updated TERMINAL_DOCKER_FORWARD_ENV
description to note auto-passthrough from skills
300964178f