Night Watch: catch docs that name things which do not exist
Generalizes the useToggle finding. That bug was not "an example broke" but "a doc
named a subject that does not exist" — a hook, component, topic, or template that
was renamed or never existed, inside an otherwise valid command.
Records the method, because the obvious approach is wrong: extracting
`astryx <cmd> <subject>` by regex and checking the subject against --list was
tried and produced 8 false findings out of 11. Aliases still resolve
(`component XDSButton` is absent from --list but exits 0 and prints the Button
doc), and ordinary prose matches the pattern ("...only contains astryx component
strings."). Executing the invocation settles both, and is what caught useToggle.
Also notes that a subject resolving only through a legacy alias is a softer
finding: it works, but it teaches the old name.
Co-authored-by: Cursor <cursoragent@cursor.com>