docs: tighten the right rail follow-up comments and drop a one-use helper

Comments that still spoke of the strip scrolling or of a lifted max-height say what the code does now; the tab and column comments are shorter; the changelog bullet is wrapped. panelDisclosure.js is back to its reviewed shape: railTabFor had one caller left after the header click handoff was reverted.

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

changelog.d/1425-right-rail-vertical-tabs.md

@@ -2,12 +2,13 @@
   Imagery while shown) is a vertical tab strip with sideways labels instead of
   an accordion of collapsed launcher cards: at most one panel is open in every
   desktop HUD layout, and the open tab and its panel share one surface and
-  outline, like a folder tab. On a short window the rail rises toward the HUD corner above it and the tabs share the room equally, clipping the longer labels, rather than scroll. A first-time visitor on a
-  desktop finds Display open; a stored choice still wins. The panels' own
-  collapse arrows are gone on desktop: the tab opens and closes a panel, and
-  Escape inside one closes it and returns focus to its tab; the strip is a
-  keyboard-navigable tablist. The compact Radio launcher moves from Context's
-  header to the bottom of the strip on desktop and always opens the compact
-  player, also while Context is open; the player's Details button leads to the
-  Radio section. Saved preferences, share links and the phone sheet shell are
-  unchanged (gekh, #1425).
+  outline, like a folder tab. On a short window the rail rises toward the HUD
+  corner above it, and the tabs then share the room equally rather than
+  scroll. A first-time visitor on a desktop finds Display open; a stored
+  choice still wins. The panels' own collapse arrows are gone on desktop: the
+  tab opens and closes a panel, Escape inside one closes it and returns focus
+  to its tab, and the strip is a keyboard-navigable tablist. The compact Radio
+  launcher moves from Context's header to the bottom of the strip on desktop
+  and always opens the compact player, also while Context is open; the
+  player's Details button leads to the Radio section. Saved preferences, share
+  links and the phone sheet shell are unchanged (gekh, #1425).

docs/CURRENT-STATE.md

@@ -1488,8 +1488,8 @@ unnecessary style writes.
 The compact Radio player is independent of Context: its launcher toggles it
 whether Context is collapsed or open, and only an outside pointer, Escape, its
 close button or its Details button closes it, never a layout pass. The
-expanded Enable's reveal of the directory and Play lands its smooth scroll
-even when a rail layout pass, measuring the panels, cuts it short.
+reveal after the expanded Enable lands its smooth scroll even when a rail
+layout pass cuts it short.
 The right rail skips panels hidden by other CSS (computed `display: none`), but
 keeps the collapsed panels its own exclusive presentation hides, so the owner
 rule can still give them back.
@@ -1510,12 +1510,11 @@ The strip is a vertical `role="tablist"`: Up/Down
 wrap, Home/End jump, the open tab (else the first) is the tab stop, Escape
 inside a panel returns focus to its tab, and the strip precedes the panels in
 the DOM so Tab from the open tab reaches the tool slot and then the panel.
-Labels are the panels' own translated header titles. The rail's lane shares
-the left rail's top; when it is too short for the strip, the rail climbs toward
-the HUD corner above as far as the strip needs (`src/ui/rightPanelRail.js`),
-and a lane still shorter is shared equally between the tabs: a label short
-enough keeps its height, the long ones end up the same height and clip at the
-end; the strip never scrolls. Under the tabs the strip's
+Labels are the panels' own translated header titles. The lane's top follows the
+left rail's; a strip taller than the lane lifts the rail toward the HUD corner
+above (`src/ui/rightPanelRail.js`), and a lane still shorter is shared equally
+between the tabs, so the long labels end up one height and clip; the strip
+never scrolls. Under the tabs the strip's
 column keeps a tool slot (`#right-rail-tools`) that holds the compact Radio
 launcher on desktop: `src/ui/radioPanelPlacement.js` moves it there from
 Context's header, and back for the phone sheet, so the compact player stays one

src/ui/panelDisclosure.js

@@ -13,13 +13,6 @@ function listenerScope() {
   };
 }
 
-/** The strip tab that controls a right-rail panel, if the panel has one. */
-function railTabFor(panel) {
-  return panel.ownerDocument?.querySelector?.(
-    `[role="tab"][aria-controls="${panel.id}"]`,
-  );
-}
-
 /** Bind collapse buttons and bubbling Escape to an existing panel. */
 export function bindPanelDisclosure({
   panel,
@@ -70,7 +63,9 @@ export function collapsePanelOnEscape(
     panel.querySelector(`[data-dock-toggle-target="${panel.id}"]`) ||
     panel.querySelector(`[data-collapse-target="${panel.id}"]`);
   // A right-rail panel collapses out of view; its tab stays and takes focus.
-  const tab = railTabFor(panel);
+  const tab = panel.ownerDocument?.querySelector?.(
+    `[role="tab"][aria-controls="${panel.id}"]`,
+  );
   const escapedFromDisclosure =
     event.target === disclosure || disclosure?.contains?.(event.target);
   if (tab) tab.focus({ preventScroll: true });

src/ui/rightPanelRail.js

@@ -174,8 +174,8 @@ export function layoutRightPanelRail({
     .map((node) => [node, node.scrollTop || 0])
     .filter(([, top]) => top > 0);
   const naturalHeights = new Map();
-  // The tab strip's column stands beside the panels at its own height; the
-  // measuring override lifts its lane clamp too.
+  // The tab strip's column stands beside the panels; the measuring override
+  // gives it its natural height.
   const column = stack.querySelector?.(':scope > #right-rail-column');
   let columnHeight = 0;
   // Remove live height allocations through a synchronous CSS override. Keeping
@@ -222,7 +222,7 @@ export function layoutRightPanelRail({
   if (!layout) return;
   // A lane too short for the strip's column: the rail climbs toward the HUD
   // above, as far as the strip needs and the obstacles allow. A lane still
-  // shorter scrolls the strip (rightRailTabs.js).
+  // shorter shrinks the tabs (styles/right-rail-tabs.css).
   const shortfall = columnHeight - (layout.safeBottom - layout.safeTop);
   if (shortfall > 0) layout = resolve(alignedTop - shortfall) || layout;
   const { safeTop, safeBottom, maxHeight: availableHeight } = layout;

src/ui/styles/right-rail-tabs.css

@@ -57,10 +57,10 @@
   }
 }
 
-/* The strip's column: the tablist, then a tool slot that holds the compact
-   Radio launcher on desktop (radioPanelPlacement.js). It stands the lane's
-   full height, which makes the strip's size definite so its tabs can share
-   it (see .right-rail-tab); only the strip and the slot take the pointer. */
+/* The strip's column: the tablist, then a tool slot for the compact Radio
+   launcher (radioPanelPlacement.js). It stands the lane's full height, which
+   makes the strip's size definite for the tabs' share (.right-rail-tab); only
+   the strip and the slot take the pointer. */
 #right-rail-column {
   position: absolute;
   top: 0;
@@ -90,8 +90,7 @@
   min-height: 0;
   /* Room for the open tab's bridge on the left. */
   padding-left: var(--right-rail-tabs-gap);
-  /* The rail climbs above its baseline to fit the column (rightPanelRail.js);
-     a lane still shorter shrinks the tabs. The strip never scrolls. */
+  /* Never a scrollbar: a lane too short shrinks the tabs (.right-rail-tab). */
   overflow: hidden;
   pointer-events: auto;
 }
@@ -168,17 +167,16 @@ body:not(.mobile-shell)
   display: none;
 }
 
-/* The strip clips overflow, so the focus ring draws inside the tab. */
+/* The tab's mask covers its own box only: the focus ring draws inside it. */
 #right-rail-tabs > .right-rail-tab:focus-visible {
   outline-offset: -3px;
 }
 
-/* A short strip is shared between the tabs: a zero basis hands the strip's
-   height out in equal parts, a tab's own length caps its part, and what a
-   short label leaves goes to the longer ones, which end up the same height. A
-   strip with room gives every tab its own length. The basis is 0%, not 0:
-   the strip's content size, which sizes the column, comes from the labels. A
-   tab clips its label at the end, faded over the bottom padding. */
+/* A short strip is shared out equally: the zero basis hands every tab the
+   same part, a tab's own length caps it, and a short label's leftover goes
+   to the longer ones; with room each tab is its own length. The basis is
+   0%, not 0, so the strip still sizes to its labels. The label clips at the
+   end, faded over the bottom padding. */
 .right-rail-tab {
   position: relative;
   display: flex;
@@ -231,7 +229,7 @@ body:not(.mobile-shell)
   text-shadow: none;
 }
 
-/* Short windows: tighter tabs before the strip has to scroll. */
+/* Short windows: tighter tabs, so fewer labels clip. */
 @media (max-height: 720px) {
   #right-rail-tabs {
     gap: 3px;