UpdatePost::execute used to return AlreadyPublished for the Published
short-circuit. This PR widened the short-circuit to four terminal
statuses and consolidated them under PostAction::Finalized — so the
old enum case stopped being emitted, and every caller already had a
defensive in_array([AlreadyPublished, Finalized], ...).
Audit before removal: nothing emits AlreadyPublished anymore (only
UpdatePost::execute returns Actions, and it returns Finalized for
the whole terminal set), no test references the case, and no string
'already_published' exists elsewhere in app/resources/tests/lang.
- Drop the enum case
- Simplify the three in_array checks to a direct === Finalized
- Delete the dead App/PostController branch that flashed the old
cannot_edit_published message (its successor branch with
cannot_edit_finalized stays). The old i18n key is left in lang/
for now — orphan but harmless, can ressuscitate if a similar
flash is added back.