Add the Browser tab: a live web page with no browser chrome

A new tab (globe, after Maps) shows one web page full-bleed in the content area —
no address bar, bookmarks or scrollbars — built for It Is Written but usable with
any page. It loads at startup and keeps running in the background.

Stage (browser-tab.js, browser-guest-preload.cjs):
- An Electron <webview> per Browser tab, in its own sandboxed process and persistent
  session. The pages live in one persistent layer inside .tab-content: every tab
  switch rebuilds .tab-content and moving a webview reloads it, so app.js now clears
  around that layer (clearTabContentKeepingBrowser).
- Tapping a text field brings up the Prayer tab's keyboard (createPrayerKeyboard with
  a sink) and types into the page with trusted input; Enter submits; the keyboard puts
  itself away when the page moves focus on (e.g. after a search). The OS touch
  keyboard is suppressed with inputmode="none" while a field is focused.
- Tapping a scripture reference opens it in a new Bible tab, in the translation
  printed beside it when that one is switched on. References are found with the app's
  own scanner: scripture-scan.js gains scanAll() (every match with its offsets),
  translationAfter() and isTranslation(); scanText/parseSlide are unchanged.
- Input inside a webview never reaches the app, so the page reports activity (idle
  splash) and five-finger touches (blank the screen) itself.
- main.cjs: webviewTag on; every webview is forced sandboxed, context-isolated, no Node,
  http(s) only, with the guest preload. No new windows (opened in place), no permission
  prompts, no downloads, no pinch-zoom, no alert/confirm/prompt boxes, and "Leave
  site?" can never block Reload or Start page. The session reports plain Chrome.
- server.js CSP: frame-src allows http(s) (a webview is a frame to CSP); style-src and
  font-src allow https (the follower's srcdoc copy inherits this policy).

Everywhere a tab kind is listed:
- app.js: create at startup and on Reset, icon, visibility defaults, + menu, fixed
  mode, no ink layer, tool handling, OSC kind + information line (the page's search
  term), phone remote scroll / tap / page buttons, OSC show / reload / home actions,
  live setting changes, translation for tapped references.
- quick-dock, tool-wheel, presentation-tools: no drawing tools on the tab.
- Phone remote: tab label, one finger scrolls the page (taps still tap), hint text;
  mirror-stream.js reports the page's scroll for the phone's local preview.
- Follower screen: the stage publishes a script-free copy of the page's DOM (only while
  a follower is linked), its scroll and form fields; the follower shows it in
  sandboxed, double-buffered frames; the relay keeps the page for late joiners.
- OSC: /bibleapp/browser, /bibleapp/browser/reload, /bibleapp/browser/home;
  tab_kind/browser feedback. Admin and phone allow-lists updated.
- Settings: Tab Visibility, a Browser Tab section (start page, page size, scripture
  taps, return to start page), Service Profiles carry its settings, OSC references.
- Admin console: show the tab, reload / start page, start page and page size.
- BROWSER_TAB.md documents it.

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

remote-state.js

@@ -22,7 +22,7 @@
   var lastSent = 0;
 
   function modeLabel(mode) {
-    var map = { bible: 'Bible', announcements: 'Announce', graphics: 'Graphics', maps: 'Maps', whiteboard: 'Whiteboard', notes: 'Notes', prayer: 'Prayer', ask: 'Ask (AI)', media: 'Media', alpha: 'Alpha', ppsync: 'PP Sync' };
+    var map = { bible: 'Bible', announcements: 'Announce', graphics: 'Graphics', maps: 'Maps', browser: 'Browser', whiteboard: 'Whiteboard', notes: 'Notes', prayer: 'Prayer', ask: 'Ask (AI)', media: 'Media', alpha: 'Alpha', ppsync: 'PP Sync' };
     return map[mode] || (mode ? mode.charAt(0).toUpperCase() + mode.slice(1) : 'Tab');
   }
 
@@ -92,6 +92,7 @@
       var title = modeLabel(t.mode);
       if (t.mode === 'bible' && t.book) title = t.book + ' ' + (t.chapter || 1);
       if (t.ppsync && t.book) title = 'PP Sync: ' + t.book + ' ' + (t.chapter || 1);
+      if (t.mode === 'browser' && t.browserLabel) title = 'Browser: ' + t.browserLabel;
       /*
        * book/chapter/verse/translation are structured fields, not just the display title. The admin
        * console needs them to (a) clone the live TV state into its private copy exactly and (b) diff