Pin zensical==0.0.31 to fix docs build

[Erol444]

Summary

• Docs builds have been failing since v1.2.2 due to an unpinned zensical dependency picking up a breaking release
• zensical 0.0.32 (Apr 7) and 0.0.33 (Apr 14) introduced a regression in nav parsing that fails on bare string entries in nav children (e.g. section index pages), causing a TypeError: Unknown nav item value type: <class 'NoneType'> during zensical build
• Pins zensical==0.0.31 (Apr 1) which is the last working version

Test plan

• Verify the docs CI workflow passes on this branch

🤖 Generated with Claude Code

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.