Set low urgency for immediate-feedback notifications (#5056)

Some users may choose to disable notification timeout for normal-level
notifications to ensure no notifications are missed when the user is
away from the screen. However, there are several Omarchy notifications
that only serve as an immediate feedback for a user action, such as
"Screensaver enabled" or "Editing config file foo.conf", for which
disabling the timeout is not desirable. This commit drops the urgency
level for such notification to low, allowing configuring a different
timeout value for them.

Notifications with an explicitly set timeout are excluded from this
commit.

config/omarchy/hooks/font-set.sample

@@ -4,4 +4,4 @@
 # To put it into use, remove .sample from the name.
 
 # Example: Show the name of the theme that was just set.
-# notify-send "New font" "Your new font is $1"
+# notify-send -u low "New font" "Your new font is $1"

config/omarchy/hooks/post-update.sample

@@ -4,4 +4,4 @@
 # To put it into use, remove .sample from the name.
 
 # Example: Show notification after the system has been updated.
-# notify-send "Update Performed" "Your system is now up to date"
+# notify-send -u low "Update Performed" "Your system is now up to date"

config/omarchy/hooks/theme-set.sample

@@ -4,4 +4,4 @@
 # To put it into use, remove .sample from the name.
 
 # Example: Show the name of the theme that was just set.
-# notify-send "New theme" "Your new theme is $1"
+# notify-send -u low "New theme" "Your new theme is $1"