feat(view): paint the whole card in one delegate

Replaces SubjectDelegate. The tag chips come home from the view: the strip was
painted there only because a delegate cannot paint outside its column and the
strip spanned all five, and with one column there is nothing to span.

RowStyleDelegate is inherited rather than dropped. Its job survives the
redesign: Qt resolves ForegroundRole into the palette's Text roles and prefers
those over HighlightedText, so the read/unread dimming would win on a selected
row and land as grey on the highlight. What it loses is the rest of its body,
which aligned cells against a text band and centred two marker columns; both
described a grid that no longer exists.

A reply's Re: prefix is stripped here. Every reply repeating the thread's
subject is the visual signature of a table of records, which is the thing item
53 is about.

The account chip becomes a bar down the card's left edge, and the reply spines
inherit its colour, so an expanded thread is bounded by one accent from its root
to its last reply without a second line in the gutter. Neither uses the raw
account colour: that colour is chosen to be a chip's fill with legible text on
top, and the same value as a thin line has to be followable down an expansion
without competing with the senders, so it is blended toward the palette's Base
by the weight threadLineColour() already uses. A reply resolves its THREAD's
colour by walking to the root, since AccountColourRole is empty on a message
row and a neutral spine under an accented root would break the continuous edge.

The build is red at this commit; the view and window still name the old
delegate.

1 files changed, 2 insertions, 54 deletions

diff --git a/src/tagchip.h b/src/tagchip.h
index 3145358..5514cae 100644
--- a/src/tagchip.h
+++ b/src/tagchip.h
@@ -59,8 +59,8 @@ void paint(QPainter *painter, const QRect &rect, const QString &text,
 /// the selection highlight it lands as grey on the highlight colour, close to
 /// unreadable.
 ///
-/// Applied to the columns that have no delegate of their own; SubjectDelegate
-/// inherits it for the subject column.
+/// Inherited by CardDelegate, which is the only delegate the thread list
+/// installs.
 class RowStyleDelegate : public QStyledItemDelegate
 {
     Q_OBJECT
@@ -72,55 +72,3 @@ protected:
                          const QModelIndex &index) const override;
 };
 
-/// Item delegate for the subject column: draws the account chip in front of
-/// the subject text, so which mailbox a thread came from reads at a glance
-/// without a tags column spelling it out.
-/// **Install on the subject column only.** It reads AccountLabelRole, which is
-/// a property of the row rather than of a cell, so as a view-wide delegate it
-/// draws the account chip into every column.
-class SubjectDelegate : public RowStyleDelegate
-{
-    Q_OBJECT
-public:
-    using RowStyleDelegate::RowStyleDelegate;
-
-    void paint(QPainter *painter, const QStyleOptionViewItem &option,
-               const QModelIndex &index) const override;
-    QSize sizeHint(const QStyleOptionViewItem &option,
-                   const QModelIndex &index) const override;
-
-    /// Vertical breathing room above the subject and below the pill row.
-    static constexpr int kRowPadding = 4;
-
-    /// How far a reply row is indented under its thread.
-    ///
-    /// Deliberately far wider than Qt's 20px default. A thread row carries an
-    /// account chip in front of its subject and a reply row does not, so a
-    /// reply's text starts about a chip's width to the LEFT of its thread's
-    /// before any indent is applied. 20px does not cover that, and the replies
-    /// come out looking flush or outdented; this has to beat a chip's width to
-    /// read as nesting at all.
-    static constexpr int kReplyIndent = 72;
-
-    /// Horizontal room reserved in front of a thread's subject for the
-    /// expander glyph the delegate draws.
-    static constexpr int kExpanderWidth = 18;
-
-    /// The font the pill strip is drawn in: a size down from the row's own.
-    ///
-    /// At the same size the pills read as a second row of content competing
-    /// with the subject, rather than as annotation beneath it. Derived from
-    /// the row font rather than fixed, so it follows the desktop's font size.
-    static QFont pillFont(const QFont &rowFont);
-
-    /// The height every row gets, tall enough for the subject and a pill strip
-    /// beneath it. The view applies this itself: a QTableView takes one height
-    /// for the whole row, so leaving it to a single column's sizeHint would
-    /// let whichever column the view happens to ask decide.
-    static int rowHeightFor(const QFont &rowFont);
-
-protected:
-    /// The height of the band the subject text occupies. Everything below it
-    /// belongs to ThreadListView's row-wide pill strip.
-    static int subjectBandHeight(const QStyleOptionViewItem &option);
-};