feat(secubox-core): Add triple-pulse LED heartbeat with staggered cascade

Implements organic "bump-bump-bump (pause)" pattern across 3 RGB LEDs:
- LED1 (health) leads the pulse sequence
- LED2 (threat) follows with offset timing (décalé)
- LED3 (capacity) trails as final beat in cascade
- Smooth intensity transitions between beats
- Subtle breathing effect during rest period
- Event pulse override preserved for alerts

Pattern timing: beat1 → gap → beat2 → gap → beat3 → rest (0.15s ticks)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package/secubox/secubox-core/root/usr/sbin/secubox-core

@@ -1094,30 +1094,139 @@ led_event_pulse() {
     return 0
 }
 
+# Triple-pulse heartbeat with staggered cascade across LEDs
+# Creates organic "bump-bump-bump (pause)" pattern
+# Each LED pulses sequentially with offset timing (décalé)
+LED_PULSE_PHASE=0  # Tracks which LED is in primary pulse
+
+led_triple_pulse() {
+    local led_num="$1"
+    local r="$2" g="$3" b="$4"
+    local intensity="$5"  # 0-100 for pulse strength
+
+    # Calculate dimmed color based on intensity
+    local ri=$((r * intensity / 100))
+    local gi=$((g * intensity / 100))
+    local bi=$((b * intensity / 100))
+
+    led_set_rgb "$led_num" "$ri" "$gi" "$bi"
+}
+
 # Fast LED heartbeat background loop
-# Runs independently at 1.5s intervals for reactive visual feedback
+# Runs independently with triple-pulse cascade effect
-# led1: Global health status
+# led1: Global health status (primary pulse)
-# led2: Security threat level
+# led2: Security threat level (offset pulse)
-# led3: Global capacity meter (CPU + Network) with event pulse overlay
+# led3: Global capacity meter (trailing pulse)
-# Reads from pre-computed cache files (no subprocess calls)
+# Pattern: bump1-bump2-bump3 (pause) with staggered timing
 led_heartbeat_loop() {
     local status_file="/tmp/secubox/led-status"
     echo "healthy" > "$status_file"
 
+    # Base colors for each LED (set by status)
+    local r1=0 g1=255 b1=0  # Health: green
+    local r2=0 g2=255 b2=0  # Threat: green
+    local r3=0 g3=255 b3=0  # Capacity: green
+
+    # Pulse timing (in 0.1s units for fine control)
+    local beat_gap=1     # Gap between beats in triple
+    local cycle_pause=8  # Pause after triple (longer rest)
+    local tick=0         # Current tick in cycle
+
     while true; do
         local status=$(cat "$status_file" 2>/dev/null || echo "healthy")
 
-        # Update RGB LEDs (reads from cache - instant)
+        # Update base colors from cache (every cycle start)
-        led_heartbeat "$status"
+        if [ "$tick" -eq 0 ]; then
+            # LED1: Health color
+            local health=$(get_health_score)
+            if [ "$health" -ge 80 ]; then
+                r1=0; g1=255; b1=50
+            elif [ "$health" -ge 50 ]; then
+                r1=255; g1=200; b1=0
+            else
+                r1=255; g1=30; b1=0
+            fi
 
-        # Check for event pulse first (overrides capacity momentarily)
+            # LED2: Threat color
-        if led_event_pulse; then
+            local threat=$(get_threat_level)
-            sleep 0.3  # Brief flash
+            if [ "$threat" -le 10 ]; then
+                r2=0; g2=255; b2=0
+            elif [ "$threat" -le 40 ]; then
+                r2=200; g2=255; b2=0
+            elif [ "$threat" -le 70 ]; then
+                r2=255; g2=150; b2=0
+            else
+                r2=255; g2=0; b2=0
+            fi
+
+            # LED3: Capacity color (from cache)
+            local cap=$(get_capacity)
+            if [ "$cap" -le 30 ]; then
+                r3=0; g3=255; b3=100
+            elif [ "$cap" -le 60 ]; then
+                r3=100; g3=255; b3=0
+            elif [ "$cap" -le 80 ]; then
+                r3=255; g3=200; b3=0
+            else
+                r3=255; g3=80; b3=0
+            fi
         fi
 
-        # Global capacity on led3
+        # Check for event pulse (overrides normal pattern)
-        led_global_capacity
+        if led_event_pulse; then
-        sleep 1.2
+            sleep 0.3
+            tick=0
+            continue
+        fi
+
+        # Triple-pulse cascade pattern with décalé (staggered) timing
+        # Cycle: 0=beat1, 1=gap, 2=beat2, 3=gap, 4=beat3, 5-12=rest
+        local total_cycle=$((3 + 2 * beat_gap + cycle_pause))
+        local phase=$((tick % total_cycle))
+
+        # Calculate intensities for each LED based on phase
+        # LED1 leads, LED2 offset by 1 beat, LED3 offset by 2 beats
+        local int1=30 int2=30 int3=30  # Base dim level
+
+        case "$phase" in
+            0)  # First beat - LED1 bright, others dim
+                int1=100
+                ;;
+            1)  # Gap - LED1 fading, LED2 rising
+                int1=60
+                int2=80
+                ;;
+            2)  # Second beat - LED2 bright, LED1 dim, LED3 rising
+                int1=40
+                int2=100
+                int3=60
+                ;;
+            3)  # Gap - LED2 fading, LED3 rising
+                int2=60
+                int3=80
+                ;;
+            4)  # Third beat - LED3 bright, others dim
+                int3=100
+                ;;
+            5)  # Post-triple fade
+                int1=20; int2=20; int3=50
+                ;;
+            *)  # Rest period - all dim with subtle breathing
+                local breath=$((30 + (phase % 3) * 5))
+                int1=$breath; int2=$breath; int3=$breath
+                ;;
+        esac
+
+        # Apply intensities
+        led_triple_pulse 1 "$r1" "$g1" "$b1" "$int1"
+        led_triple_pulse 2 "$r2" "$g2" "$b2" "$int2"
+        led_triple_pulse 3 "$r3" "$g3" "$b3" "$int3"
+
+        tick=$((tick + 1))
+        [ "$tick" -ge "$total_cycle" ] && tick=0
+
+        # Fine timing: 0.15s per tick for smooth animation
+        sleep 0.15
     done
 }