docs: kdoc: finish disentangling the BODY and SPECIAL_SECTION states
Move the last SPECIAL_SECTION special case into the proper handler
function, getting rid of more if/then/else logic. The leading-space
tracking was tightened up a bit in the move. Add some comments describing
what is going on.
No changes to the generated output.
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250621203512.223189-10-corbet@lwn.net