Timers: LTC is listener-only; admin switch, device/channel, grouped settings

Simplify LTC to its one working source — the built-in audio listener — and
make the admin UI reflect it.

Module:
- Remove the stage-display websocket source (stage-ws.js, stagePassword)
  and the /v1/timecode/status API probe — both dead on ProPresenter 21.4.
- Remove the remote-reader ingest (POST /ltc, ingestToken, tools/
  ltc-reader.js): the module owns LTC end to end now. The decoder selftest
  moves to modules/propresenter-timers/ltc.selftest.js so the engine stays
  covered.
- composeLtc collapses to the listener: running/stopped/nosignal, or a
  clear note when disabled / no device / capture failed / starting.
- Manifest: ltcEnabled is now a `switch`; ltcDevice and ltcChannel carry
  showWhen:"ltcEnabled"; ProPresenter and LTC fields carry `group` labels.

Shell (admin) — backward-compatible additions, coordinate with the shell lane:
- New `switch` field type (boolean shown as the enable-toggle control).
- `group`: consecutive fields render under a labeled subsection.
- `showWhen: "<key>"`: a field is shown only while that boolean/switch is
  on (and actually collapses — .field[hidden] override, since .field's
  display:flex outranks the [hidden] UA default).
- applyConfigPatch coerces `switch` as boolean. Documented in MODULE-GUIDE.

Verified: engine selftest (29 checks); listener decodes BlackHole loopback
(running 30fps, ageMs); device picker lists inputs; POST /ltc now 404s;
admin shows two labeled groups, the switch, and device/channel appearing
only when the switch is on (computed display none↔flex confirmed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/propresenter-timers/module.json

@@ -7,53 +7,41 @@
   "client": "client.js",
   "server": "server.js",
   "style": "style.css",
-  "minSize": {
-    "w": 2,
-    "h": 1
-  },
-  "defaultSize": {
-    "w": 4,
-    "h": 2
-  },
+  "minSize": { "w": 2, "h": 1 },
+  "defaultSize": { "w": 4, "h": 2 },
   "configSchema": {
     "propresenter": {
       "type": "endpoint",
       "label": "ProPresenter",
-      "default": {
-        "host": "",
-        "port": 1025
-      }
+      "group": "ProPresenter",
+      "default": { "host": "", "port": 1025 }
     },
     "password": {
       "type": "password",
       "label": "API password (only if set in ProPresenter)",
+      "group": "ProPresenter",
       "default": ""
     },
     "ltcEnabled": {
-      "type": "boolean",
+      "type": "switch",
       "label": "LTC listener — decode timecode from an audio input on this machine",
+      "group": "LTC Timecode",
       "default": false
     },
     "ltcDevice": {
       "type": "select",
-      "label": "LTC audio device",
+      "label": "Audio device",
+      "group": "LTC Timecode",
+      "showWhen": "ltcEnabled",
       "default": "",
       "optionsRoute": "/ltc/devices"
     },
     "ltcChannel": {
       "type": "number",
-      "label": "LTC channel on that device (1-based)",
+      "label": "Channel on that device (1-based)",
+      "group": "LTC Timecode",
+      "showWhen": "ltcEnabled",
       "default": 1
-    },
-    "ingestToken": {
-      "type": "password",
-      "label": "LTC reader token (optional — for tools/ltc-reader.js on another machine)",
-      "default": ""
-    },
-    "stagePassword": {
-      "type": "password",
-      "label": "Stage display password (LTC fallback via a stage field labeled \"LTC\")",
-      "default": ""
     }
   }
 }