PTP: drop the "Preferred TimeTransmitter" role

It behaved exactly like auto (clock class 248); the only difference was a
priority1 suggestion in the page. Roles are now slave|auto; to prefer this
device, use auto with a low priority1. A stored "master" is converted to
auto at boot (new cfg_set_string, like cfg_set_number).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/index.html

@@ -105,8 +105,7 @@ e.g. curl -X POST http://p4-aes67.local/api/player/next
   <small>hybrid: Delay_Req/Resp unicast</small></label>
 <label><span>Role</span><select name="ptp.role">
   <option value="slave">TimeReceiver only</option>
-  <option value="auto">Auto (TimeTransmitter if none)</option>
-  <option value="master">Preferred TimeTransmitter</option></select></label>
+  <option value="auto">Auto (TimeTransmitter if none)</option></select></label>
 <label><span>Domain</span><input name="ptp.domain" type="number" min="0" max="127"></label>
 <label><span>Priority 1</span><input name="ptp.priority1" type="number" min="0" max="255"></label>
 <label><span>Priority 2</span><input name="ptp.priority2" type="number" min="0" max="255"></label>
@@ -291,7 +290,7 @@ const CORE_DEF = {
   log:{syslog:false,host:'',port:514,level:'info',facility:'16',format:'rfc5424'}
 };
 // Priority1 suggested when the role is changed in the UI (user can still edit it).
-const ROLE_P1 = {auto:250, master:100};
+const ROLE_P1 = {auto:250};
 // PTP presets. riedel = Riedel Director defaults for a SIC AES67 card.
 const PTP_PRESETS = {
   riedel: {mode:'multicast', role:'slave', domain:0, priority1:128, priority2:126,
@@ -302,7 +301,7 @@ function ptpPreset(name) {
   for (const [k, v] of Object.entries(PTP_PRESETS[name])) f['ptp.' + k].value = v;
   toggle(); sdp(); msg.textContent = `Loaded ${name} PTP defaults – Save to apply.`;
 }
-const CLOCK_CLASS = {slave:255, auto:248, master:248};
+const CLOCK_CLASS = {slave:255, auto:248};
 
 const $ = id => document.getElementById(id);
 const f = $('f'), sdpEl = $('sdp'), msg = $('msg');