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, 19 insertions, 12 deletions

diff --git a/src/carddelegate.h b/src/carddelegate.h
index 7012eaa..74dee8e 100644
--- a/src/carddelegate.h
+++ b/src/carddelegate.h
@@ -52,20 +52,27 @@ public:
     static QRect expanderRectFor(const QStyleOptionViewItem &option,
                                  const QModelIndex &index);
 
-    /// The colour the accent bar is painted in: the account's own, undiluted.
+    /// The colour the accent bar is painted in: the account's hue, lifted to a
+    /// floor of saturation and lightness.
     ///
-    /// Blending it toward the palette's Base was tried first, at the 0.35
-    /// weight threadLineColour() uses, and produced an INVISIBLE bar on a dark
-    /// theme: against a Base of (0.169, 0.169, 0.169) it landed at (0.18, 0.22,
-    /// 0.26), which is the background. The weight is a fraction OF THE ACCOUNT
-    /// COLOUR, so a low one keeps the background rather than the hue.
+    /// Two earlier versions were wrong in opposite directions. Blending toward
+    /// the palette's Base at threadLineColour()'s 0.35 weight produced an
+    /// INVISIBLE bar on a dark theme, landing at (0.18, 0.22, 0.26) against a
+    /// Base of (0.169, 0.169, 0.169): the weight is a fraction OF THE ACCOUNT
+    /// COLOUR, so a low one keeps the background rather than the hue. Passing
+    /// the raw colour through fixed that and was still too quiet, because an
+    /// account colour is chosen as a CHIP's fill with legible text on top and
+    /// is therefore mid-tone by construction.
     ///
-    /// An account colour is already chosen to be a chip's fill with legible
-    /// text on top, so it is muted to begin with; three pixels of a muted
-    /// colour is nothing. Nothing is drawn on this bar, so it needs none of the
-    /// contrast that choice was made for. The SPINE is where the muting belongs
-    /// and is blended in paint(): it runs the full height of every reply in an
-    /// expansion and has to be followable without competing with the senders.
+    /// A floor, not a repaint: a colour already past it is returned untouched,
+    /// so a deliberately vivid choice is preserved. Hue is never altered, since
+    /// hue is the whole information the bar carries and a shifted one would
+    /// stop matching the account's chip and its swatch in the dropdown.
+    ///
+    /// The SPINE takes its colour from this and mutes it again in paint(): it
+    /// runs the full height of every reply in an expansion and has to be
+    /// followable without competing with the senders, which is a different
+    /// problem from a 3px edge marker.
     ///
     /// Falls back to threadLineColour() for a thread with no account tag.
     static QColor accentLineColour(const QColor &accountColour);