add Mom/Tog to ToggleWidget, Big Title, Layout panel scaffold

- ToggleWidget: add Momentary/Toggle mode selector (mirrors TransportWidget
  minus OSC); HW routing respects trigger_mode; fix invisible button on init
  by removing explicit empty stylesheet; saves/loads trigger_mode per preset
- Big Title: full-width 28px bold QLineEdit above fader row, saves per-preset
  as big_title; green underline on focus; single bottom border, no separator
- Layout panel: floating 220px window to the left of main window, toggled by
  new Layout button next to Messages; shows Sections checkboxes (Preset
  Browser, Big Title, Fader Row, Toggle Row, Transport Row); tracks window
  move/resize; checkboxes not yet wired to functionality

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

presets/presets.json

@@ -1,5 +1,5 @@
 {
-  "__last_used__": "preset3",
+  "__last_used__": "preset5",
   "presets": {
     "preset1": {
       "faders": [
@@ -244,7 +244,22 @@
           "zone_index": -1
         }
       ],
-      "toggles": [],
+      "toggles": [
+        {
+          "uid": "e291394c-cc09-4d3c-9ac3-ed5fe2803a46",
+          "label": "Toggle 1",
+          "cc": 20,
+          "ch": 1,
+          "state": false,
+          "color": "Gray",
+          "zone": null,
+          "center_index": null,
+          "zone_index": null,
+          "hw_cc": null,
+          "hw_channel": null,
+          "trigger_mode": "toggle"
+        }
+      ],
       "browser": {
         "back": {
           "label": "Back",
@@ -398,7 +413,8 @@
           "center_index": null,
           "zone_index": null,
           "hw_cc": null,
-          "hw_channel": null
+          "hw_channel": null,
+          "trigger_mode": "toggle"
         }
       ],
       "browser": {
@@ -419,6 +435,7 @@
           "trigger_mode": "momentary"
         }
       },
+      "big_title": "STRING SHORTS",
       "preset_uuid": "3e9d51d2-cf55-49f4-80a4-2f7f4466f959",
       "show_hide": {
         "fader": false,
@@ -510,10 +527,10 @@
       "trigger_mode": "momentary"
     }
   ],
-  "transport_show_hide": false,
+  "transport_show_hide": true,
   "io_config": {
     "midi_out": "IAC Driver Bus 5",
-    "midi_in": "VMPK Output",
+    "midi_in": "Not Connected",
     "transport_out": "Not Connected",
     "osc_ip": "127.0.0.1",
     "osc_listen_port": 9000,