fix(tabs): grouped rail editing review fixes

- Pointer drag: a press released outside the rail no longer lingers. The
  release is heard on window while a press is pending, a move with the
  primary button up cancels it, a new press cancels any previous drag, and
  an existing Escape listener is removed before another is added, so no
  orphaned capture listener can swallow Escape before the terminal.
- Inline group rename: a commit by blur leaves focus where the user put it;
  Enter and Escape still return focus to the header.
- A failed layout read while edits are pending keeps the held layout and the
  editor and re-reads once the write settles, so a 409 is still rebased.
  Dropping unsaved work now always says so in a toast.
- "Move to <group>" quotes the group name (with a matching zh-CN pattern), so
  a group named "New group" or "ungrouped" no longer reads or translates like
  the fixed entries.
- The group menu glyph stays visible under (hover: none).
- The sessionStorage replay copy carries { owner, baseVersion, savedAt } and is
  ignored for another owner, after 60 s, or against an older layout. A move
  with no anchor carries no index, so a replay keeps the row last.
- A 400 that survives the re-read is reported as "Could not save tab groups."
- closeTabRailActionMenu() no longer removes the group menu's DOM.
- Cancelling "Delete group" returns focus to the header.
- Stale comments updated.

src/web/public/styles.css

@@ -752,6 +752,14 @@ html[data-tab-orientation='vertical'] .tab-rail .tab-layout-group-header:focus-v
   opacity: 1;
 }
 
+/* No hover on a touch tablet, and a long press there is not a contextmenu
+   event: the glyph is the only way into the group menu, so keep it shown. */
+@media (hover: none) {
+  html[data-tab-orientation='vertical'] .tab-rail .tab-layout-group-menu {
+    opacity: 1;
+  }
+}
+
 html[data-tab-orientation='vertical'] .tab-rail .tab-layout-group-menu:hover {
   color: var(--text);
   background: var(--bg-tertiary, var(--bg-hover));