docs: searchfold and linecap are the only components with no page

[OsherElhadad]

searchfold and linecap are the only two registered components without a page under
docs/components/. All 22 registered components are documented — both have rows in
docs/components.md (:15, :26) and ### sections (:156, :319) — but 20 of 22 also have
a dedicated page wired into the mkdocs nav, and these two do not.

This is an information-architecture inconsistency rather than a documentation hole, but it is
about to become more visible: #142 corrects the preset table, which adds searchfold and
linecap to nine rows. Nine rows will then name two components a reader cannot click, while
cacheinject (in no preset) and toon (retired from every preset) both have full pages.

Suggested fix: two stub pages following the existing docs/components/*.md shape, moving
the components.md ### sections into them.