settings: one snackbar for every page's messages

Save, apply and upload results went to the page header, one line capped
at 420px and cut with an ellipsis. They now go to a snackbar at the foot
of the settings window, wrapped in full: green fades after 6s, yellow and
red stay until dismissed or replaced, and changing page clears it.

Snack.qml is the singleton pages call (ok, wait, error); Snackbar.qml
draws it once in Settings.qml. SaveBar forwards its notice and error, so
the 24 pages using it change nothing; the header keeps only the draft's
state. The boot logo page calls Snack directly.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/desktop/README.md b/desktop/README.md
index c7aea52..9e17e7a 100644
--- a/desktop/README.md
+++ b/desktop/README.md
@@ -56,6 +56,15 @@ page's draft lives in the page, so it is not marked in the sidebar and
 leaving the page drops it. Git and autostart act a row at a time and the
 theme applies on click, so they have no bar.
 
+What a save, an apply or an upload says goes to the snackbar at the foot of
+the window (`Snack.qml`, drawn by `Snackbar.qml`), in full and wrapped: green
+fades after 6s, yellow (waiting) and red (failed) stay until dismissed with
+its cross or replaced by the next message. Changing page or closing the
+window clears it. SaveBar forwards its `notice` and `error` there, so a page
+using it needs nothing more; any other page calls `Snack.ok(text)`,
+`Snack.wait(text)` or `Snack.error(text)`. The header keeps only the draft's
+state beside the buttons: "unsaved changes", or why Save is held back.
+
 The sidebar's edge drags to resize it, between 160 and 420px; the width is
 saved in the preferences file on release.