Phase 1/2: .desktop launcher, volume control in deskbar

- Launcher now loads apps dynamically from /usr/share/applications
  and ~/.local/share/applications instead of a hardcoded list;
  maps desktop Categories to tab system, falls back to built-in list
  on systems without .desktop files (dev/macOS builds)
- Launcher gains scroll support: mouse wheel and PgUp/PgDn scroll
  the app grid, scrollbar drawn on right edge when needed
- Deskbar status bar shows VOL % from pactl (cached, polls every 5s)
- Deskbar status bar: scroll wheel changes volume ±5%, left-click
  toggles mute

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

deskbar/src/deskbar.c

@@ -161,6 +161,23 @@ static int read_cpu_percent(void) {
     return (int)(100 * (d_total - d_idle) / d_total);
 }
 
+static int read_volume_percent(void) {
+    static int cached = -1;
+    static int ticks  = 0;
+    if (ticks-- > 0) return cached;
+    ticks = 4;  /* re-poll every 5 seconds */
+    FILE *f = popen("pactl get-sink-volume @DEFAULT_SINK@ 2>/dev/null", "r");
+    if (!f) return cached;
+    char line[256];
+    cached = -1;
+    if (fgets(line, sizeof(line), f)) {
+        char *p = strstr(line, "/ ");
+        if (p) cached = atoi(p + 2);
+    }
+    pclose(f);
+    return cached;
+}
+
 static int read_battery_percent(void) {
     FILE *f;
     char path[80];
@@ -422,16 +439,20 @@ void db_draw(Deskbar *db) {
         int  mem = read_mem_percent();
         int  bat = read_battery_percent();
         char bst = read_battery_status();
-        char status[64];
+        int  vol = read_volume_percent();
+        char status[80];
         int  pos = 0;
+        if (vol >= 0)
+            pos += snprintf(status + pos, sizeof(status) - pos,
+                            "VOL %d%%", vol);
         if (cpu >= 0)
             pos += snprintf(status + pos, sizeof(status) - pos,
-                            "CPU %d%%", cpu);
+                            "%sCPU %d%%", pos ? "  " : "", cpu);
         if (mem >= 0)
             pos += snprintf(status + pos, sizeof(status) - pos,
                             "  MEM %d%%", mem);
         if (bat >= 0) {
-            const char *arrow = (bst == 'C') ? "↑" : (bst == 'F') ? "=" : "↓";
+            const char *arrow = (bst == 'C') ? "+" : (bst == 'F') ? "=" : "-";
             pos += snprintf(status + pos, sizeof(status) - pos,
                             "  BAT %d%%%s", bat, arrow);
         }
@@ -888,8 +909,24 @@ void db_run(Deskbar *db) {
                 if (e.xexpose.count == 0) db_draw(db);
                 break;
             case ButtonPress:
-                if (e.xany.window == db->win)
-                    db_click(db, e.xbutton.x, e.xbutton.y);
+                if (e.xany.window == db->win) {
+                    int sy = db_status_y(db);
+                    if (e.xbutton.button == Button4) {
+                        /* scroll up on status bar = volume up */
+                        if (e.xbutton.y >= sy)
+                            system("pactl set-sink-volume @DEFAULT_SINK@ +5% 2>/dev/null &");
+                        break;
+                    }
+                    if (e.xbutton.button == Button5) {
+                        if (e.xbutton.y >= sy)
+                            system("pactl set-sink-volume @DEFAULT_SINK@ -5% 2>/dev/null &");
+                        break;
+                    }
+                    if (e.xbutton.button == Button1 && e.xbutton.y >= sy)
+                        system("pactl set-sink-mute @DEFAULT_SINK@ toggle 2>/dev/null &");
+                    else
+                        db_click(db, e.xbutton.x, e.xbutton.y);
+                }
                 break;
             case MotionNotify:
                 if (e.xany.window == db->win)