docs: update docs with renovate

[jon4hz]

Summary

s/Dependabot/Renovate/g

Closes #

Type of Change

• 🐛 Bug fix — patch version bump
• ✨ New workflow — minor version bump
• 🔧 Update existing workflow — patch or minor version bump
• 🗑️ EOL / deprecate workflow
• 📖 Documentation only
• 🔒 Security improvement
• 🤖 Dependency / tooling update

Checklist

• Workflow YAML is created or updated under .github/workflows/
• Documentation is created or updated under docs/workflows/ (or docs/actions/)
• Permissions table in docs/security/permissions.md is updated
• zensical.toml nav is updated (required when a docs page is added or removed)
• AGENTS.md is updated (required when repository structure or conventions change)
• A smoke-test job exists (or the exception is documented)
• All caller examples include permissions: {} at the workflow level with explicit per-job permissions
• All third-party actions are pinned to a full commit SHA with version tag comment (e.g. @abc1234 # v3)
• Any new third-party actions have been evaluated against the action selection criteria
• No new known-vulnerable dependencies have been introduced (check Dependabot alerts and the thresholds)
• For breaking changes: migration guidance is included in the docs and the commit message contains BREAKING CHANGE:
• For EOL: deprecation notice is added to the workflow YAML and docs