swarm-ui: a hide debug output toggle in the header's settings menu

The row moves from the per-agent page into @hive/shared so both pages mount
the same one. The terminal's debug rows now follow the preference as it
changes, so rows already on screen hide or show at once instead of only the
rows that arrive after the toggle.

frontend/packages/swarm-ui/src/shell/Shell.tsx

@@ -32,6 +32,7 @@ import { Link, useLocation } from "wouter-preact";
 import { LinksMenu } from "./LinksMenu.js";
 import { UserMenu } from "./UserMenu.js";
 import { SettingsMenu } from "@hive/shared/settings-menu.js";
+import { HideDebugSetting } from "@hive/shared/hide-debug-setting.js";
 import { useApplyThemeOverride } from "@hive/shared/theme-apply.js";
 import { useApplyMotionOverride } from "@hive/shared/motion-apply.js";
 import { useDynamicTabs } from "./useDynamicTabs.js";
@@ -444,7 +445,9 @@ export function Shell({ children }: { children: ComponentChildren }) {
             `margin-left: auto` split the available space between them
             instead of sitting flush together at the right edge. */}
         <div class="shell-header-actions">
-          <SettingsMenu themeKey={THEME_KEY} motionKey={MOTION_KEY} />
+          <SettingsMenu themeKey={THEME_KEY} motionKey={MOTION_KEY}>
+            <HideDebugSetting />
+          </SettingsMenu>
           <LinksMenu />
           <UserMenu />
         </div>