Carry over what only the win7 tree had: middle-click close, ARIA, menu fix

The deleted win7 tree held a few behaviours the modern tree never got:

- Context menu: the first ArrowUp in a fresh menu skipped the last item
  (Delete in the row menu, Disconnect in the tab menu) — stepping from -1
  landed one short. The index math moves to core/menu-nav.ts stepIndex(),
  checked by menu-nav.spec.ts (bun test; verified to fail on the old logic).
  Items get ids and the menu exposes aria-activedescendant, so screen
  readers follow the arrow keys while focus stays on the menu.
- Middle-click closes a tab, as in browsers. auxclick also fires for the
  right button, so only button 1 counts; closeWorkspace already refuses the
  last tab. A middle press is swallowed so WebView2 doesn't start autoscroll
  over the scrollable strip. The hover ✕ stays.
- ARIA: the tab strip is a tablist of role=tab buttons with aria-selected
  (the in-tab ✕ is taken out of the a11y tree and tab order — Ctrl/Cmd+W and
  the tab menu remain the keyboard paths); transfer bars are progressbars
  with value and a name.

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

ui/src/app/skins/shadlike/context-menu.ts

@@ -10,6 +10,7 @@ import {
 import { NgIcon } from '@ng-icons/core';
 import { ContextMenuService, type MenuItem } from '@core/context-menu.service';
 import { FocusService } from '@core/focus.service';
+import { stepIndex } from '@core/menu-nav';
 import { remPx } from '@core/metrics';
 
 /** Rough per-item metrics in REM, used only to decide whether the menu must
@@ -38,6 +39,7 @@ const EDGE_GAP = 6; // px on purpose: a viewport-edge margin, not a UI size
         #menuEl
         role="menu"
         tabindex="-1"
+        [attr.aria-activedescendant]="activeIndex() >= 0 ? 'ctx-item-' + activeIndex() : null"
         (keydown)="onKeydown($event)"
         [style.left.px]="position().x"
         [style.top.px]="position().y"
@@ -50,6 +52,7 @@ const EDGE_GAP = 6; // px on purpose: a viewport-edge margin, not a UI size
             <button
               type="button"
               role="menuitem"
+              [attr.id]="'ctx-item-' + $index"
               [title]="item.tooltip ?? ''"
               [disabled]="!!item.disabled"
               [class.bg-accent]="$index === activeIndex() && !item.disabled"
@@ -163,18 +166,9 @@ export class ContextMenu {
     }
   }
 
-  /** Move the highlight by one selectable item, skipping separators and
-   *  disabled entries, wrapping. */
-  private step(items: MenuItem[], delta: number): void {
-    const count = items.length;
-    if (!count) return;
-    let index = this.activeIndex();
-    for (let hops = 0; hops < count; hops++) {
-      index = (index + delta + count) % count;
-      if (items[index].type !== 'separator' && !items[index].disabled) {
-        this.activeIndex.set(index);
-        return;
-      }
-    }
+  /** Move the highlight by one selectable item (see stepIndex). */
+  private step(items: MenuItem[], delta: 1 | -1): void {
+    const selectable = items.map((i) => i.type !== 'separator' && !i.disabled);
+    this.activeIndex.set(stepIndex(selectable, this.activeIndex(), delta));
   }
 }

ui/src/app/skins/shadlike/tab-bar/tab-bar.ts

@@ -49,6 +49,7 @@ const CONCURRENCY_CHOICES = [2, 3, 4, 6, 8] as const;
     >
       <div
         #tabScroll
+        role="tablist"
         class="flex min-w-0 items-center gap-0.5 overflow-x-auto [scrollbar-width:none] [&::-webkit-scrollbar]:hidden"
       >
       @for (ws of panels.workspaces(); track ws.id; let i = $index) {
@@ -59,6 +60,8 @@ const CONCURRENCY_CHOICES = [2, 3, 4, 6, 8] as const;
           [class.opacity-50]="draggedId() === ws.id"
           [style.box-shadow]="dropIndicatorShadow(i)"
           (contextmenu)="onTabContextMenu($event, ws, i)"
+          (mousedown)="onTabMouseDown($event)"
+          (auxclick)="onAuxClick($event, ws.id)"
           draggable="true"
           (dragstart)="onDragStart($event, ws.id)"
           (dragover)="onDragOver($event, i)"
@@ -66,6 +69,8 @@ const CONCURRENCY_CHOICES = [2, 3, 4, 6, 8] as const;
           (dragend)="onDragEnd()"
         >
           <button
+            role="tab"
+            [attr.aria-selected]="ws.id === panels.activeWorkspaceId()"
             (click)="panels.setActiveWorkspace(ws.id)"
             class="flex min-w-0 items-center gap-1.5 py-1.5 pr-1 pl-2.5 text-xs"
             [class.text-foreground]="ws.id === panels.activeWorkspaceId()"
@@ -83,6 +88,8 @@ const CONCURRENCY_CHOICES = [2, 3, 4, 6, 8] as const;
           @if (panels.workspaces().length > 1) {
             <button
               (click)="close($event, ws.id)"
+              tabindex="-1"
+              aria-hidden="true"
               [title]="i18n.t('tabBar.closeTab', { mod: modLabel })"
               class="mr-1 grid size-4 shrink-0 place-items-center rounded text-muted-foreground opacity-0 group-hover:opacity-100 hover:bg-border hover:text-foreground"
             >
@@ -484,6 +491,22 @@ export class TabBar {
     this.panels.closeWorkspace(id);
   }
 
+  /**
+   * Middle-click closes the tab, as in browsers. `auxclick` also fires for the
+   * right button, hence the button check; the last tab is refused by
+   * closeWorkspace itself.
+   */
+  onAuxClick(event: MouseEvent, id: number): void {
+    if (event.button !== 1) return;
+    event.preventDefault();
+    this.close(event, id);
+  }
+
+  /** A middle press over the scrollable strip would start WebView2's autoscroll. */
+  onTabMouseDown(event: MouseEvent): void {
+    if (event.button === 1) event.preventDefault();
+  }
+
   /**
    * Right-click a tab. The menu targets THIS tab, not the active one — its
    * actions all carry the id — so right-clicking a background tab does not

ui/src/app/skins/shadlike/transfer-bar/transfer-bar.html

@@ -19,7 +19,14 @@
         <div class="min-w-0 flex-1">
           <div class="truncate text-[0.6875rem] text-muted-foreground">{{ progressLabel(job) }}</div>
           @if (isActive(job)) {
-            <div class="mt-0.5 h-1 overflow-hidden rounded-full bg-muted">
+            <div
+              role="progressbar"
+              aria-valuemin="0"
+              aria-valuemax="100"
+              [attr.aria-valuenow]="jobPercent(job)"
+              [attr.aria-label]="job.name"
+              class="mt-0.5 h-1 overflow-hidden rounded-full bg-muted"
+            >
               <div
                 class="h-full rounded-full bg-primary transition-[width] duration-100"
                 [style.width.%]="jobPercent(job)"