feat(ui): make the toolbar icon size configurable

Follow-up to item 56. With the toolbar now following the desktop's
button style, an "icon only" desktop makes the icon the whole control,
and this style reports PM_ToolBarIconSize as 16px, which is a small
target for a button with no text beside it.

A [general] toolbar_icon_size key, 16 to 64, defaulting to 24 rather
than to the style's own metric. Setting it to 16 restores the theme's
value.

Clamped and reported, unlike message_zoom, which documents a 0.5 to 3.0
range in the README and enforces none of it. Both ends here break the
UI that would be used to fix them: too small is an invisible icon, too
large is a toolbar taller than the window.

The unenforced message_zoom range is recorded as item 58 rather than
fixed here, since it is a separate defect that predates this change.

Also documents in the README that saved-query button labels are the key
names from the user's own [queries] section, which is why the "Flagged"
button still read that way after the action was renamed: it is a user's
query name, not a string this code owns. The sample config now shows
`Important = tag:flagged` to teach the wording the UI uses.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/config.h b/src/config.h
index 3174a03..3dd9011 100644
--- a/src/config.h
+++ b/src/config.h
@@ -90,6 +90,18 @@ public:
     /// Empty when unset; the caller disables the Sync button in that case.
     QString syncCommand() const { return m_syncCommand; }
 
+    /// Toolbar icon size in pixels, 16 to 64, defaulting to 24.
+    ///
+    /// The desktop's own PM_ToolBarIconSize was the obvious default and was
+    /// rejected empirically: it reports 16 here, which is a small target now
+    /// that the toolbar follows the platform's "icon only" style and the icon
+    /// is the whole control. Setting this to 16 restores the theme's value.
+    ///
+    /// Clamped rather than trusted: a 4px icon is invisible and a 4000px one
+    /// makes the toolbar taller than the window, and neither is recoverable
+    /// from the UI the value just broke.
+    int toolbarIconSize() const { return m_toolbarIconSize; }
+
     /// The sync script's log file, read to learn the outcome of a sync this
     /// process did not start (item 54).
     ///
@@ -171,6 +183,7 @@ private:
     QList<SavedQuery> m_savedQueries;
     QString m_syncCommand;
     QString m_syncLog;
+    int m_toolbarIconSize = 24;
     QString m_notmuchConfig;
     qreal m_messageZoom = 1.0;
     bool m_completionOnFocus = false;