refactor(ui): trim the right rail tabs surface, share one DOM fake and one phone breakpoint

rightRailTabs.js exports only createRightRailTabs, nextRailTabIndex and railJoinPath and returns element, sync and destroy; the id constants, railTabPanels, the argument guard and the createElementNS fallback existed for the tests alone. The sub-720px density tier and the slot's focus ring go; the five rail cards carry data-rail-card so the stylesheet lists them once.

src/ui/mobileShellContract.js holds the phone shell's media query and class, dependency-free so the rail layout and panel packages can read them; rightPanelRail.js, panelPositionControls.js and radioPanelPlacement.js use it instead of their own literals. src/testSupport/fakeDom.mjs replaces the two hand-made DOM fakes of the rail and strip tests; the rail tests now expect null for a missing attribute, as in the DOM. The two Radio gate checks of the removed several-panels rail policy are gone.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

scripts/package-boundaries.json

@@ -424,6 +424,7 @@
       "src/ui/displayPanelScroll.js",
       "src/ui/leftPanelRail.js",
       "src/ui/rightPanelRail.js",
+      "src/ui/mobileShellContract.js",
       "src/ui/panelMeasurement.js",
       "src/ui/panelRailGeometry.js",
       "src/panelStackLayout.js"
@@ -762,6 +763,7 @@
       "src/ui/radioTunerModel.js",
       "src/ui/recordingControls.js",
       "src/ui/rightPanelRail.js",
+      "src/ui/mobileShellContract.js",
       "src/ui/rightRailTabs.js",
       "src/ui/sceneControls.js",
       "src/ui/scenePresentation.js",
@@ -2288,6 +2290,7 @@
       "src/ui/radioTunerModel.js",
       "src/ui/recordingControls.js",
       "src/ui/rightPanelRail.js",
+      "src/ui/mobileShellContract.js",
       "src/ui/rightRailTabs.js",
       "src/ui/sceneControls.js",
       "src/ui/scenePresentation.js",
@@ -3308,6 +3311,7 @@
       "src/hudLayouts.js",
       "src/hudLayoutPolicy.js",
       "src/ui/radioPanelPlacement.js",
+      "src/ui/mobileShellContract.js",
       "src/bloom.js",
       "src/cockpitVisionPolicy.js",
       "src/contactsDetectionPolicy.js",
@@ -3354,6 +3358,7 @@
       "src/ui/panelRailGeometry.js",
       "src/ui/panelRails.js",
       "src/ui/rightPanelRail.js",
+      "src/ui/mobileShellContract.js",
       "src/ui/rightRailTabs.js",
       "src/ui/uiLifetime.js",
       "src/i18n/index.js",

scripts/qa-radio.mjs

@@ -1902,18 +1902,6 @@ async function main() {
 
       return result;
     });
-    check(
-      'HUD-off desktop lanes keep Data plus Scenes and Display plus Context expanded inside the viewport corridor',
-      multiExpandedPanelLayout.independentLeft
-        && multiExpandedPanelLayout.independentRight
-        && multiExpandedPanelLayout.leftCountsAllExpanded
-        && multiExpandedPanelLayout.rightCountsAllExpanded
-        && multiExpandedPanelLayout.leftInsideCorridor
-        && multiExpandedPanelLayout.rightInsideCorridor
-        && multiExpandedPanelLayout.internalScrollOwned
-        && multiExpandedPanelLayout.restoredExactly,
-      JSON.stringify(multiExpandedPanelLayout),
-    );
     check(
       'HUD-off to Tactical preserves the latest-opened Scenes panel and hides its collapsed Data competitor',
       multiExpandedPanelLayout.tacticalAutoCollapse.latestOpenedPanel === 'scene-panel'
@@ -1927,16 +1915,6 @@ async function main() {
         && multiExpandedPanelLayout.tacticalAutoCollapse.contextAriaExpanded === 'false',
       JSON.stringify(multiExpandedPanelLayout.tacticalAutoCollapse),
     );
-    check(
-      'closing Tactical lane owners restores eligible temporary siblings without changing disclosure truth',
-      multiExpandedPanelLayout.tacticalAutoRestore.dataExpanded
-        && multiExpandedPanelLayout.tacticalAutoRestore.dataAutoMarkerCleared
-        && multiExpandedPanelLayout.tacticalAutoRestore.dataAriaExpanded === 'true'
-        && multiExpandedPanelLayout.tacticalAutoRestore.contextExpanded
-        && multiExpandedPanelLayout.tacticalAutoRestore.contextAutoMarkerCleared
-        && multiExpandedPanelLayout.tacticalAutoRestore.contextAriaExpanded === 'true',
-      JSON.stringify(multiExpandedPanelLayout.tacticalAutoRestore),
-    );
     check(
       'Tactical Display hides ordinary collapsed CCTV and Context launchers',
       Object.values(multiExpandedPanelLayout.tacticalDisplayExclusive).every(Boolean),