Prelude docs in a consumer repo

Treat the user's argument as the task description (e.g. "add a recipes page under a Guides group"), not a shell command. Manage the requested Markdown sources and existing prelude.docs.* configuration; preserve unrelated settings.

Prerequisite: the repo imports prelude.flakeModules.default (see the prelude-install skill). The docs viewer has no enable flag — it activates automatically when prelude.docs.pages is non-empty, which also installs the docs command, its x docs dispatch, and the d accelerator.

Authored pages

prelude.docs.pages is a nav tree in declaration order. Every node is exactly one of leaf / group / generate: