0.1.3: load notes from the page

Loading notes should not have been a terminal command, and now it is not.

The empty board carries the door: "No notes yet. Point Tiiny Brain at a folder
of markdown", with a button. The same button sits in the top bar and the same
panel is under Settings. Give it a folder, or browse to one from this machine,
and one press runs the walk, the filing, the chunking, the embedding on your
Tiiny and the name index, telling you which of the five it is on. The board
redraws itself when it finishes. Point it at the same folder later and it only
does what changed.

The five commands still work exactly as they did. They are just no longer the
only way in.

Every step that cannot run now says which step and keeps what came before it: a
Tiiny nobody has set up, a Tiiny that did not answer, a Tiiny answering and
serving no embedding model, a folder with no markdown. The names are built
either way, so a sleeping Tiiny costs you the ability to ask and nothing else,
and try again picks up where it stopped. An empty board is never left without
words on it.

Three faults turned up on the way and are fixed here: a load started before the
device was configured used to leave the page saying "loading" for ever; the
board could stay empty after a load while the numbers under it counted the new
notes; and the two routes the page polls no longer wait on the database during
the slowest step. Two different vaults with an Inbox at the top now stay two
notes.

PDFs in the folder are counted and reported as not loaded in this build.

Python standard library only. No subprocess anywhere in the shipped tree.