Convert British spellings to American across the repo

colour -> color, behaviour -> behavior, centre -> center, favourite ->
favorite, and about twenty other pairs, applied consistently across
comments, docs, error/UI copy, and a handful of QML identifiers that
used the British spelling as their actual name: SystemSettings'
serialiseValue/serialiseTable/normaliseGradient, Displays'
normaliseModes, Wallpaper's normalisePolicy, SettingsBackup's
serialiseHomeState, DateTime's ntpSynchronised property, Clipboard's
_normalise helper, and ShortcutCapture's cancelled signal (with its
onCancelled handler in ShortcutsPage.qml). Every call site and the two
tests that assert on the literal source text (settings-ownership and
settings-backup-live contracts) were updated in lockstep.

Left untouched: config/dot/espanso/match/packages/misspell-en/ is a
vendored third-party autocorrect dictionary -- its entries are typo
corrections, not our prose, and rewriting them would fight the
package's own purpose (and any future re-sync from upstream).

The already-American `favorites` property (Home page pinned
accessories) was never actually misspelled -- only nearby comments and
error strings said "favourites" -- so no data migration was needed
there.

Claude-Session: https://claude.ai/code/session_01E6TJUAh41HaP25MVHWkhRZ

config/dot/quickshell/modules/bar/Bar.qml

@@ -10,7 +10,7 @@
 //       Bar {}
 //   }
 //
-// Layout mirrors GNOME's: workspaces + vitals left, clock + weather centre,
+// Layout mirrors GNOME's: workspaces + vitals left, clock + weather center,
 // media + tray + status cluster right.
 
 import Quickshell
@@ -83,7 +83,7 @@ PanelWindow {
             }
         }
 
-        // ── Centre ──────────────────────────────────────────────────────────
+        // ── Center ──────────────────────────────────────────────────────────
         Row {
             anchors.horizontalCenter: parent.horizontalCenter
             anchors.verticalCenter: parent.verticalCenter

config/dot/quickshell/modules/bar/Clock.qml

@@ -1,4 +1,4 @@
-// The centre clock, kept in the same place and the same format GNOME had it:
+// The center clock, kept in the same place and the same format GNOME had it:
 // weekday, date, 12-hour time with seconds. Clicking it opens the calendar,
 // exactly like GNOME's date menu.
 
@@ -35,7 +35,7 @@ Pill {
         anchors.verticalCenter: parent.verticalCenter
         text: Qt.formatDateTime(clock.date, root.format)
         font.family: Theme.fontFamily
-        // Seconds tick once a second in the centre of the bar; without tabular
+        // Seconds tick once a second in the center of the bar; without tabular
         // figures the whole clock shifts sideways on every digit change.
         font.features: Theme.tabularFigures
         font.pixelSize: Theme.fontSize

config/dot/quickshell/modules/bar/StatusCluster.qml

@@ -62,7 +62,7 @@ Pill {
             if (!root.wifiNetwork)
                 return "\u{F092D}";              // md-wifi_strength_off
 
-            // NetworkManager reports strength 0-100; some backends normalise to
+            // NetworkManager reports strength 0-100; some backends normalize to
             // 0-1, so accept either rather than showing one bar forever.
             const raw = root.wifiNetwork.signalStrength ?? 0;
             const strength = raw <= 1 ? raw * 100 : raw;

config/dot/quickshell/modules/bar/VitalsField.qml

@@ -1,5 +1,5 @@
 // One glyph + percentage pair inside VitalsWidget. Split out so the three
-// fields cannot drift apart in spacing, width or colour thresholds.
+// fields cannot drift apart in spacing, width or color thresholds.
 
 import QtQuick
 import qs.config

config/dot/quickshell/modules/bar/VitalsWidget.qml

@@ -2,7 +2,7 @@
 // Vitals extension was configured with (_processor_usage_, _memory_usage_,
 // _gpu#1_usage_).
 //
-// Values are colour-coded rather than graphed: at bar size a number you can
+// Values are color-coded rather than graphed: at bar size a number you can
 // glance at beats a sparkline you have to squint at.
 
 import QtQuick

config/dot/quickshell/modules/bar/Workspaces.qml

@@ -36,7 +36,7 @@ Item {
 
     implicitWidth: row.implicitWidth + 12
     // Full bar height makes (0, 0) part of the wheel target. The dots stay
-    // optically centred by the row and active-pill geometry below.
+    // optically centered by the row and active-pill geometry below.
     implicitHeight: Theme.barHeight
 
     // Scroll over the padding either side of the row, not just over a dot.
@@ -59,7 +59,7 @@ Item {
         border.width: 0 // QTBUG-137166: rounded rects can lose their corners
 
         // The prism, as a fill rather than a hairline. This is the one element
-        // in the bar that is always coloured, so it is where the pair belongs.
+        // in the bar that is always colored, so it is where the pair belongs.
         gradient: Gradient {
             orientation: Gradient.Horizontal
             GradientStop {