dream: plan Material for MkDocs → Zensical migration before EOL

[franccesco]

Dream finding 019 (planning)

Umbrella: #20 | Dream: dream-2026-07-23.1

Material for MkDocs entered maintenance mode (9.7.0); official support commitment ~12 months from 2025-11-05 (~EOL 2026-11-05). Successor: Zensical.

After the 9.7.7 security pin lands, track migration for mkdocs.yml + mkdocstrings + GH Pages workflow.

Refs:

• https://squidfunk.github.io/mkdocs-material/blog/2025/11/05/zensical/
• https://squidfunk.github.io/mkdocs-material/changelog/#9.7.0

Nothing auto-merges — planning only.