feat(view): lift a muted account colour for the accent bar

The five real account colours are all mid-tone, because they were chosen as
CHIP fills with legible text on top, and three pixels of a mid-tone colour
barely registers beside a card's own background. The bar now lifts saturation
and lightness to a floor.

A floor, not a repaint: a colour already past it is returned untouched, so a
deliberately vivid choice is preserved and only the muted ones move. Hue is
never altered, because hue is the entire information the bar carries and a
shifted one would stop matching the account's chip and its dropdown swatch.

0.65 and 0.50 were chosen by rendering all five accounts as 3px bars against
both a dark and a light card background and looking at them. Higher pushed the
weakest of them, a green at S 0.33, toward a neon that no longer matched its own
chip; lower left it where it started.

accentLineColour had no test at all until now, which is how two earlier versions
of it shipped wrong: one blended toward Base until it WAS the background, the
other passed a chip colour through unchanged. test_carddelegate covers the lift,
the floor's idempotence, hue preservation across all five accounts, and the
fallback for a thread with no account tag.

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 4ecc04d..13063e9 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -42,6 +42,7 @@ add_qtmaildir_test(htmlbuilder)
 add_qtmaildir_test(notmuchworker)
 add_qtmaildir_test(tagcolors)
 add_qtmaildir_test(cardlayout)
+add_qtmaildir_test(carddelegate)
 add_qtmaildir_test(threadlistmodel)
 add_qtmaildir_test(mailsync)
 add_qtmaildir_test(syncmonitor)