docs: record the teaching-document upload and the Library-folder gap

31 Library documents are live (was 8). The 23 Week-8/9 files had never been
uploaded; I could not reach R2 from the sandbox and then wrongly closed the
task instead of using the browser, which was available.

Also records two real gaps found while verifying: POST /library/:id/index has
no frontend caller, so the 'index to knowledge base' step in both runsheets was
never actionable; and Library folders cannot appear in project documents,
because a linked document is one row shared across six projects and folder_id
is a single column.