feat(keyboard): add Cmd+./Ctrl+. shortcut to toggle both sidebars

Reassign Cmd+. (Mac) and Ctrl+. (Win/Linux) from toggling the left
sidebar to toggling both sidebars at once. If either is open, both
close; if both are closed, both open. Left sidebar toggle on non-Mac
now uses Ctrl+B to match the Mac Cmd+B binding.

packages/app/src/keyboard/actions.ts

@@ -35,6 +35,7 @@ export type KeyboardActionId =
   | "workspace.navigate.relative"
   | "sidebar.toggle.left"
   | "sidebar.toggle.right"
+  | "sidebar.toggle.both"
   | "command-center.toggle"
   | "shortcuts.dialog.toggle"
   | "workspace.terminal.new"

packages/app/src/keyboard/keyboard-shortcuts.ts

@@ -649,22 +649,16 @@ const SHORTCUT_BINDINGS: readonly ShortcutBinding[] = [
       keys: ["mod", "B"],
     },
   },
-  {
-    id: "sidebar-toggle-left-cmd-period-mac",
-    action: "sidebar.toggle.left",
-    combo: "Cmd+.",
-    when: { mac: true, commandCenter: false },
-  },
   {
     id: "sidebar-toggle-left-ctrl-period-non-mac",
     action: "sidebar.toggle.left",
-    combo: "Ctrl+.",
+    combo: "Ctrl+B",
     when: { mac: false, commandCenter: false, terminal: false },
     help: {
       id: "toggle-left-sidebar",
       section: "panels",
       label: "Toggle left sidebar",
-      keys: ["mod", "."],
+      keys: ["mod", "B"],
     },
   },
   {
@@ -698,6 +692,32 @@ const SHORTCUT_BINDINGS: readonly ShortcutBinding[] = [
     when: { hasSelectedAgent: true, commandCenter: false },
   },
 
+  // --- Toggle both sidebars ---
+  {
+    id: "sidebar-toggle-both-cmd-period-mac",
+    action: "sidebar.toggle.both",
+    combo: "Cmd+.",
+    when: { mac: true, commandCenter: false },
+    help: {
+      id: "toggle-both-sidebars",
+      section: "panels",
+      label: "Toggle both sidebars",
+      keys: ["mod", "."],
+    },
+  },
+  {
+    id: "sidebar-toggle-both-ctrl-period-non-mac",
+    action: "sidebar.toggle.both",
+    combo: "Ctrl+.",
+    when: { mac: false, commandCenter: false, terminal: false },
+    help: {
+      id: "toggle-both-sidebars",
+      section: "panels",
+      label: "Toggle both sidebars",
+      keys: ["mod", "."],
+    },
+  },
+
   // --- Message input ---
   {
     id: "message-input-voice-toggle-cmd-shift-d-mac",