Fix the dead win7 context menu, flatten the selection, add a tab menu

Right-click did nothing under the win7 skin, and then swallowed the next
click. 7.css declares `position: relative` on ul[role=menu] and the `skin`
layer outranks `utilities`, so Tailwind's `.fixed` lost: [style.left/top.px]
became flow offsets from the menu's static position — the last child of the
h-screen frame — and every menu rendered below the viewport, unreachable
behind overflow:hidden. Its backdrop is a plain <div>, unmatched by 7.css, so
that stayed genuinely fixed and ate the following click. Regressed in 0ae2a62,
when the menu adopted 7.css's real markup.

Restated `position: fixed` in skinfix, scoped to a new `w7-ctx` marker so
7.css's own menus keep theirs. scripts/menu-probe.ts is the regression test:
it renders the menu at declared coordinates, pixel-scans whether it landed
there, and carries a marker-less control menu (the bug verbatim) as its own
discriminator. A resting pixel diff cannot see this class of bug.

Selection band goes flat: --w7-sel-bg/-bd (#cbe8f6/#26a0da) is what Explorer
actually painted, where 7.css reused --w7-el-grad-h, its Aero element-hover
ramp. That var is left alone — buttons and tabs still want the gloss. The
unfocused pane gets the grey idle band; the band still never disappears with
focus, it only weakens. Harness diff confirms the change touches selection
rows and nothing else, in both themes.

New workspace-tab right-click menu in both skins: New Tab, Close Tab, Close
Other Tabs, Close Tabs to the Right, Disconnect. The target id travels inside
the action string because the right-clicked tab is not necessarily the active
one. Illegal entries are disabled rather than omitted, the way Win7 greyed
out — and since 7.css's [aria-disabled] handling is CSS-only, the keyboard
paths check the flag themselves.

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

ui/src/app/skins/shadlike/app.ts

@@ -121,6 +121,10 @@ export class App {
       this.settings.toggleColumn(action.slice('col:'.length) as ColumnKey);
       return;
     }
+    if (action.startsWith('tab:')) {
+      this.handleTabAction(action.slice('tab:'.length));
+      return;
+    }
     if (action.startsWith('open-stack:')) {
       const id = action.slice('open-stack:'.length);
       let stackConnections = this.connections.connections().filter((c) => c.stackId === id);
@@ -197,6 +201,35 @@ export class App {
   }
 
   /** Context-menu actions apply to the row/panel remembered at right-click time. */
+  /**
+   * Workspace-tab menu actions. The target id travels INSIDE the action string
+   * because the right-clicked tab is not necessarily the active one — nothing
+   * here may fall back to activeWorkspaceId.
+   */
+  private handleTabAction(action: string): void {
+    if (action === 'new') {
+      this.panels.newWorkspace();
+      return;
+    }
+    const parsed = /^([a-z-]+):(\d+)$/.exec(action);
+    if (!parsed) return;
+    const id = Number(parsed[2]);
+    switch (parsed[1]) {
+      case 'close':
+        this.panels.closeWorkspace(id);
+        break;
+      case 'close-others':
+        this.panels.closeOtherWorkspaces(id);
+        break;
+      case 'close-right':
+        this.panels.closeWorkspacesToRight(id);
+        break;
+      case 'disconnect':
+        void this.panels.disconnectWorkspace(id);
+        break;
+    }
+  }
+
   private handleContextAction(action: string): void {
     const target = this.actions.menuTarget;
     if (!target) return;