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/scripts/panama-settings-backup

@@ -135,7 +135,7 @@ def valid_home(value: Any) -> bool:
 
 def validate_home(value: Any, label: str) -> dict[str, Any]:
     if not valid_home(value):
-        fail(f"{label} does not contain valid Home favourites.")
+        fail(f"{label} does not contain valid Home favorites.")
     return value
 
 

config/dot/quickshell/scripts/panama-theme-apps

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-# Propagates the colour scheme to applications that do not read the desktop
+# Propagates the color scheme to applications that do not read the desktop
 # portal.
 #
 # Most modern applications DO follow org.freedesktop.portal.Settings and need
@@ -47,7 +47,7 @@ esac
 
 # Same 8 named accents as config/Theme.qml's `accents` map (kept in sync by
 # hand -- there is no shared source between QML and a shell script), primary
-# hue per scheme only: both consumers below draw a flat colour, not the
+# hue per scheme only: both consumers below draw a flat color, not the
 # two-stop gradient the window border does.
 accent_hex() {
     local name="$1" scheme="$2"
@@ -108,7 +108,7 @@ status_hyprlock="skipped"
 if [[ -r "$lock_template" ]]; then
     # Written atomically: a lock triggered mid-write would otherwise read a
     # truncated config and fall back to hyprlock's own defaults, which is a
-    # bright grey screen with none of this desktop's identity.
+    # bright gray screen with none of this desktop's identity.
     if sed -e "s/@FG@/$lock_fg/g" \
            -e "s/@MUTED@/$lock_muted/g" \
            -e "s/@ACCENT@/$lock_accent/g" \
@@ -159,7 +159,7 @@ fi
 # it on the next write.
 #
 # btop reads its theme once at startup, so a running instance keeps the old
-# colours until it is restarted. That is acceptable for a monitor you open when
+# colors until it is restarted. That is acceptable for a monitor you open when
 # you want it, and forcing a restart would kill a process the user is watching.
 btop_conf="${XDG_CONFIG_HOME:-$HOME/.config}/btop/btop.conf"
 btop_theme="tokyonight-moon"