feat(notify): add --silent flag, volume knob, and level sound files

The touchpad toggle's notification was too loud, and the eight notify sounds varied by ~13 dB in RMS loudness — bug and fail came out two to three times louder than info or security.

I added a --silent flag to notify (shows the popup, plays no sound) and a NOTIFY_VOLUME knob (paplay scale, default 65536) so the master level can drop without re-encoding. toggle-touchpad now passes --silent on both enable and disable. normalize-notify-sounds.sh measures each .ogg and shifts it to a uniform -31 dB mean. It writes through the file instead of mv-ing over it, so the stow symlinks survive when the script runs against the live sound dir. I re-encoded all eight sounds to the new level.

Tests: a new tests/notify suite (12 tests) covers --silent, the volume knob, flag composition, and the error paths.

9 files changed, 35 insertions, 8 deletions

diff --git a/dotfiles/common/.local/bin/notify b/dotfiles/common/.local/bin/notify
index a89a3ff..6918e01 100755
--- a/dotfiles/common/.local/bin/notify
+++ b/dotfiles/common/.local/bin/notify
@@ -3,7 +3,7 @@
 # notify - Display notifications with icons and sounds
 #
 # Usage:
-#   notify <type> "title" "body" [--persist]
+#   notify <type> "title" "body" [--persist] [--silent]
 #
 # Types:
 #   success  - Green checkmark, pleasant chime
@@ -17,12 +17,17 @@
 #
 # Options:
 #   --persist  Don't auto-dismiss (stays until manually closed)
+#   --silent   Show the notification but play no sound
+#
+# Environment:
+#   NOTIFY_VOLUME  Playback volume for the sound (paplay scale: 65536 = 100%).
+#                  Lower it to soften every notification without re-encoding
+#                  the sound files. Default 65536.
 #
 # Examples:
 #   notify success "Job Complete" "Download finished in 12 minutes"
 #   notify fail "Job Failed" "Connection refused" --persist
-#   notify alert "Warning" "Network speed reduced"
-#   notify question "Input Needed" "Continue or abort?"
+#   notify info "Touchpad" "Disabled" --silent
 
 set -euo pipefail
 
@@ -31,7 +36,7 @@ SOUND_DIR="$HOME/.local/share/sounds/notify"
 
 usage() {
     cat <<EOF
-Usage: notify <type> "title" "body" [--persist]
+Usage: notify <type> "title" "body" [--persist] [--silent]
 
 Types:
   success   Green checkmark, pleasant chime
@@ -45,10 +50,15 @@ Types:
 
 Options:
   --persist  Don't auto-dismiss notification
+  --silent   Show the notification but play no sound
+
+Environment:
+  NOTIFY_VOLUME  Sound playback volume (paplay scale: 65536 = 100%)
 
 Examples:
   notify success "Job Complete" "Download finished"
   notify fail "Build Failed" "Test errors" --persist
+  notify info "Touchpad" "Disabled" --silent
 EOF
     exit 1
 }
@@ -61,7 +71,24 @@ fi
 TYPE="$1"
 TITLE="$2"
 BODY="$3"
-PERSIST="${4:-}"
+shift 3
+
+# Optional flags, in any order
+PERSIST=""
+SILENT=""
+for arg in "$@"; do
+    case "$arg" in
+        --persist) PERSIST="--persist" ;;
+        --silent)  SILENT=1 ;;
+        *)
+            echo "Error: Unknown option '$arg'" >&2
+            usage
+            ;;
+    esac
+done
+
+# Master playback volume (paplay scale: 65536 = 100%)
+NOTIFY_VOLUME="${NOTIFY_VOLUME:-65536}"
 
 # Validate type and set icon/sound
 case "$TYPE" in
@@ -129,9 +156,9 @@ if [[ -f "$ICON" ]]; then
     NOTIFY_ARGS+=(--icon="$ICON")
 fi
 
-# Play sound in background (if it exists)
-if [[ -f "$SOUND" ]]; then
-    paplay "$SOUND" &
+# Play sound in background (unless silenced, and if the file exists)
+if [[ -z "$SILENT" && -f "$SOUND" ]]; then
+    paplay --volume="$NOTIFY_VOLUME" "$SOUND" &
 fi
 
 # Send notification
diff --git a/dotfiles/common/.local/share/sounds/notify/alarm.ogg b/dotfiles/common/.local/share/sounds/notify/alarm.ogg
index b4dff15..de9b0b7 100644
--- a/dotfiles/common/.local/share/sounds/notify/alarm.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/alarm.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/alert.ogg b/dotfiles/common/.local/share/sounds/notify/alert.ogg
index 217f33a..9001f2a 100644
--- a/dotfiles/common/.local/share/sounds/notify/alert.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/alert.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/bug.ogg b/dotfiles/common/.local/share/sounds/notify/bug.ogg
index 6842082..a1bfb03 100644
--- a/dotfiles/common/.local/share/sounds/notify/bug.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/bug.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/fail.ogg b/dotfiles/common/.local/share/sounds/notify/fail.ogg
index 916d88a..e4f067f 100644
--- a/dotfiles/common/.local/share/sounds/notify/fail.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/fail.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/info.ogg b/dotfiles/common/.local/share/sounds/notify/info.ogg
index 57900b4..0dc8e10 100644
--- a/dotfiles/common/.local/share/sounds/notify/info.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/info.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/question.ogg b/dotfiles/common/.local/share/sounds/notify/question.ogg
index 8e44c55..2a6017e 100644
--- a/dotfiles/common/.local/share/sounds/notify/question.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/question.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/security.ogg b/dotfiles/common/.local/share/sounds/notify/security.ogg
index 301287e..d2ecd20 100644
--- a/dotfiles/common/.local/share/sounds/notify/security.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/security.ogg
diff --git a/dotfiles/common/.local/share/sounds/notify/success.ogg b/dotfiles/common/.local/share/sounds/notify/success.ogg
index c28da65..6bf93fe 100644
--- a/dotfiles/common/.local/share/sounds/notify/success.ogg
+++ b/dotfiles/common/.local/share/sounds/notify/success.ogg