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.html

@@ -1345,6 +1345,30 @@
         momentumRaf = requestAnimationFrame(step);
       }
 
+      /*
+       * Start a scroll gesture. Two fingers anywhere; on the Browser tab ONE finger too, once it has
+       * travelled — there is nothing to draw on a web page, and one finger is how the page scrolls on the
+       * TV itself. A finger that does not travel is still a tap (mirror_tap), so buttons, the search box
+       * and scripture references stay pressable from the phone.
+       */
+      var BROWSER_SCROLL_SLOP = 0.012;   // fraction of the picture: past this, a one-finger touch is a drag
+      function beginScroll(touches, oneFinger) {
+        scroll.active = true;
+        scroll.oneFinger = !!oneFinger;
+        scroll.lastY = avgY(touches);
+        scroll.total = 0;
+        scroll.seq = 0;
+        scroll.gesture = ++gestureCounter;
+        scrollAnchor = wanted;      // the finger takes over from here (null until a stamped frame)
+        scrollSpeed = 0;
+        scroll.samples = [{ t: Date.now(), y: scroll.lastY }];
+        redrawStrokes();  // synchronous: wipe a cancelled live stroke off the mirror right now
+        paintPreview();
+      }
+      function hintText() {
+        return activeTabMode() === 'browser' ? 'tap to press \u00b7 drag to scroll' : 'tap to press \u00b7 1 finger draws \u00b7 2 fingers scroll';
+      }
+
       pad.addEventListener('touchstart', function (e) {
         e.preventDefault();
         var wasCoasting = !!momentumRaf;
@@ -1371,16 +1395,7 @@
           // the app discards it the same way it discards a two-finger-cancelled stroke on the TV.
           if (stroke.sent) queueDraw('cancel', []);
           resetStroke();
-          scroll.active = true;
-          scroll.lastY = avgY(e.touches);
-          scroll.total = 0;
-          scroll.seq = 0;
-          scroll.gesture = ++gestureCounter;
-          scrollAnchor = wanted;      // the finger takes over from here (null until a stamped frame)
-          scrollSpeed = 0;
-          scroll.samples = [{ t: Date.now(), y: scroll.lastY }];
-          redrawStrokes();  // synchronous: wipe a cancelled live stroke off the mirror right now
-          paintPreview();
+          beginScroll(e.touches, false);
           return;
         }
         if (scroll.active) return;
@@ -1390,9 +1405,9 @@
         var mode = activeTabMode();
         var tool = tvToolNow();
         // Match the TV's own refusals up front, so the preview never shows a line the TV will not draw:
-        // no drawing on announcement/graphics/maps tabs, no drawing with a non-drawing tool, and a
+        // no drawing on announcement/graphics/maps/browser tabs, no drawing with a non-drawing tool, and a
         // stroke must START inside the text area (the TV ignores ones that don't).
-        var blocked = (mode === 'announcements' || mode === 'graphics' || mode === 'maps')
+        var blocked = (mode === 'announcements' || mode === 'graphics' || mode === 'maps' || mode === 'browser')
           || !(tool === 'pen' || tool === 'highlight' || tool === 'erase');
         var r = tvRect();
         if (!blocked && r && (p.x < r.x || p.x > r.x + r.w || p.y < r.y || p.y > r.y + r.h)) blocked = true;
@@ -1408,7 +1423,7 @@
         if (swallowGesture) return;
         var now = Date.now();
         if (scroll.active) {
-          if (e.touches.length < 2) return;
+          if (e.touches.length < (scroll.oneFinger ? 1 : 2)) return;
           var y = avgY(e.touches);
           var movedPx = y - scroll.lastY;
           scroll.lastY = y;
@@ -1426,6 +1441,13 @@
         var p = norm(e.touches[0]);
         if (!p) return;
         if (stroke.blocked) {
+          if (activeTabMode() === 'browser') {
+            var f0 = stroke.all[0];
+            if (Math.abs(p.x - f0.x) < BROWSER_SCROLL_SLOP && Math.abs(p.y - f0.y) < BROWSER_SCROLL_SLOP) return;   // still a tap
+            resetStroke();
+            beginScroll(e.touches, true);
+            return;
+          }
           // Tell the operator once WHY nothing is happening instead of silently eating the gesture.
           if (!stroke.warned) {
             stroke.warned = true;
@@ -1512,7 +1534,7 @@
           hint.textContent = 'Splash is on — tap the screen to hide it';
           hint.style.opacity = '1';
         } else if (!hintIntro) {
-          hint.textContent = 'tap to press · 1 finger draws · 2 fingers scroll';
+          hint.textContent = hintText();
           hint.style.opacity = '0';
         }
       }
@@ -1536,7 +1558,7 @@
         view.classList.remove('hidden');
         setStatus('connecting…', '');
         hintIntro = true;
-        hint.textContent = 'tap to press · 1 finger draws · 2 fingers scroll';
+        hint.textContent = hintText();
         hint.style.opacity = '1';
         setTimeout(function () { hintIntro = false; updateTvHint(); }, 2600);
         updateTvHint();