Content-area double-click over "dead" page space toggles the hybrid host's maximize; triple-click toggles fullscreen. Suppressed over editable/interactive targets (input/textarea/select/button/link/contenteditable/widget-roles, shadow- DOM-aware via composedPath) and when the multi-click selects text (double-click- a-word / triple-click-a-line), so ordinary selection never resizes the window. Detection lives content-side in the universal preload (runtime-external-preload.cjs) — the only realm with the DOM target + live selection; main's input-event stream has clickCount but no target. Rides Chromium's native multi-click counter (MouseEvent.detail), no timers/debounce (fsm-pilled). New main module hybrid-window-gesture.ts maps detent 2 -> maximize, 3 -> fullscreen; maximize is routed back through the shared chrome overlay (page:request-toggle-maximize) so the overlay stays the single source of truth for maximize state + chrome reflow. Scope: covers http(s) page-host content (hybrid WebContentsView). peek:// tiles use a different preload and are not covered by this pass.