feat(lotus): layout, settings and reactions over the widget API (cinny #43)

The Lotus host drove these by clicking EC's hidden controls in our DOM and
read screenshare/layout state from it, which only works while the frame is
same-origin and breaks whenever a data-testid changes. New actions:

- toWidget io.lotus.set_layout { layout: "grid" | "spotlight" } → the layout
  switch view model's setLayout.
- toWidget io.lotus.open_settings { open?: boolean } → setSettingsOpen
  (toggle when `open` is omitted).
- toWidget io.lotus.toggle_reactions → a window event the reactions button
  listens for.
- fromWidget io.lotus.controls_state { screensharing, layout } on change; its
  arrival tells the host the fork supports the actions above.

Screensharing stays host-driven for now: getDisplayMedia needs the user's
click to reach this frame (Capability Delegation), which a widget message
doesn't carry.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/lotus/lotusActions.ts

@@ -62,6 +62,24 @@ export enum LotusWidgetActions {
    * else in the call (#39). Each fires at most once per share.
    */
   ScreenshareNotice = "io.lotus.screenshare_notice",
+  /**
+   * toWidget: switch the call layout `{ layout: "grid" | "spotlight" }`
+   * (cinny #43 — replaces the host clicking EC's hidden layout radio).
+   */
+  SetLayout = "io.lotus.set_layout",
+  /**
+   * toWidget: open EC's settings modal, or close it with `{ open: false }`;
+   * omit `open` to toggle (cinny #43).
+   */
+  OpenSettings = "io.lotus.open_settings",
+  /** toWidget: toggle the reactions / raise-hand menu (cinny #43). */
+  ToggleReactions = "io.lotus.toggle_reactions",
+  /**
+   * fromWidget: `{ screensharing: boolean, layout: "grid" | "spotlight" | null }`
+   * whenever either changes (cinny #43), so the host stops reading EC's DOM for
+   * them. Its arrival also tells the host this fork supports the actions above.
+   */
+  ControlsState = "io.lotus.controls_state",
 }
 
 /** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */
@@ -72,4 +90,7 @@ export const LOTUS_TO_WIDGET_ACTIONS: LotusWidgetActions[] = [
   LotusWidgetActions.Decorations,
   LotusWidgetActions.SetDeafen,
   LotusWidgetActions.SetAudioOutput,
+  LotusWidgetActions.SetLayout,
+  LotusWidgetActions.OpenSettings,
+  LotusWidgetActions.ToggleReactions,
 ];