Two boot/panel UX changes that share the editor's constructor, so they
land in one commit:
- Power-on mode is now Normal (was Insert). with_text() opens a loaded
note in Normal with the caret on the last char (the resume point);
draw(false) now suppresses the caret in every mode, so the boot-error
screen renders as pure text rather than sprouting a block caret.
- notice/set_notice(): a transient side-panel message ("snackbar")
drawn under the word count and cleared on the next keystroke — no
timed repaint, which on e-ink would cost a ~630 ms flash to erase.
e797381da6