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

tests/quickshell/lock-screen-theme-contract.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-# The lock screen follows the colour scheme.
+# The lock screen follows the color scheme.
 #
 # It did not. hyprlock.conf shipped with Tokyo Night Moon hardcoded in six
 # places, so choosing light mode left the one screen a user sees most often
@@ -26,11 +26,11 @@ fail() {
 
 [[ -r "$template" ]] || fail 'hyprlock.conf.template is missing, so nothing generates the lock screen'
 
-# The committed template must carry no literal colours. One left behind is a
-# colour that silently stays dark in light mode -- exactly the original bug.
+# The committed template must carry no literal colors. One left behind is a
+# color that silently stays dark in light mode -- exactly the original bug.
 literal="$(grep -vE '^\s*#' "$template" | grep -oE 'rgba\([0-9]+, *[0-9]+, *[0-9]+' || true)"
 [[ -z "$literal" ]] \
-    || fail "the template still contains hardcoded colours, which will not follow the scheme: $literal"
+    || fail "the template still contains hardcoded colors, which will not follow the scheme: $literal"
 
 fixture="$(mktemp -d /tmp/panama-lockscreen.XXXXXX)"
 trap 'rm -rf "$fixture"' EXIT
@@ -44,31 +44,31 @@ for scheme in dark light; do
     [[ -r "$generated" ]] || fail "no hyprlock.conf was generated for $scheme"
 
     # An unsubstituted placeholder is not a parse error to hyprlock; it is an
-    # invalid colour it quietly ignores, falling back to its own default.
+    # invalid color it quietly ignores, falling back to its own default.
     leftover="$(grep -oE '@[A-Z_]+@' "$generated" || true)"
     [[ -z "$leftover" ]] \
         || fail "$scheme left placeholders unsubstituted: $leftover"
 
-    # Every colour hyprlock is given must be a complete decimal triple. It
+    # Every color hyprlock is given must be a complete decimal triple. It
     # takes rgba(r, g, b, a), NOT hex, and a hex value here is silently ignored.
-    while read -r colour; do
-        [[ -n "$colour" ]] || continue
-        grep -qE '^rgba\([0-9]{1,3}, [0-9]{1,3}, [0-9]{1,3}$' <<<"$colour" \
-            || fail "$scheme produced a malformed colour: $colour"
+    while read -r color; do
+        [[ -n "$color" ]] || continue
+        grep -qE '^rgba\([0-9]{1,3}, [0-9]{1,3}, [0-9]{1,3}$' <<<"$color" \
+            || fail "$scheme produced a malformed color: $color"
     done < <(grep -vE '^\s*#' "$generated" | grep -oE 'rgba\([^)]*' | sed 's/,[^,]*$//')
 
     # The Pango markup values are hex, and hyprlock wants them doubled-hashed.
     while read -r pango; do
         [[ -n "$pango" ]] || continue
         grep -qE '^##[0-9a-f]{6}$' <<<"$pango" \
-            || fail "$scheme produced malformed Pango markup colour: $pango"
+            || fail "$scheme produced malformed Pango markup color: $pango"
     done < <(grep -vE '^\s*#' "$generated" | grep -oE '##[0-9a-fA-F]{6}')
 
     # The whole background block, not a fixed number of lines after it: the
-    # colour sits near the end, after the blur and noise settings.
+    # color sits near the end, after the blur and noise settings.
     background="$(awk '/^background \{/,/^\}/' "$generated" \
         | grep -vE '^\s*#' | grep -oE 'color = rgba\([0-9]+' | grep -oE '[0-9]+$' | head -1)"
-    [[ -n "$background" ]] || fail "$scheme produced no background colour"
+    [[ -n "$background" ]] || fail "$scheme produced no background color"
 
     # The point of the whole exercise: a light lock screen must actually be
     # light. 128 splits the two cleanly for these palettes.