feat(app): wire the voyage together

Controller drives world and curtain; caption with Back to sea; play,
previous and next in the timeline bar; keyboard; no-WebGL frieze stage.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/controller.ts

@@ -7,12 +7,14 @@ export interface ControllerWorld {
   sailTo(songId: string, opts?: { instant?: boolean }): Promise<void>;
   setLanding(id: LandingId | null): Promise<void>;
   setRibbons(motifIds: string[] | null, highlight: string | null): void;
+  horizonFromFrieze(groundYpx: number): void;
 }
 /** The parts of the frieze curtain the controller drives (src/app/frieze/curtain.ts). */
 export interface ControllerCurtain {
   drop(sagaId: PlaceId, opts?: { landing?: LandingId }): Promise<void>;
   lift(): Promise<void>;
   fade(): Promise<void>;
+  groundY(): number;
 }
 
 export interface Controller {
@@ -23,6 +25,11 @@ export interface Controller {
   stop(): void;
   playing(): boolean;
   onPlayingChange(fn: (playing: boolean) => void): void;
+  /** The landing the stage is in, if any. */
+  landing(): LandingId | null;
+  /** "Back to sea": leave the landing, keep the song. */
+  leaveLanding(): Promise<void>;
+  onLandingChange(fn: (landing: LandingId | null) => void): void;
 }
 
 const PLAY_HOLD_MS = 3400;
@@ -30,7 +37,8 @@ const PLAY_HOLD_MS = 3400;
 /**
  * Moves the stage when the song changes. Steps run one at a time; a newer request makes the running step
  * stop at its next await, and the last request wins. A curtain left down by a cancelled step is lifted by
- * the next one, so rapid navigation never leaves the stage covered.
+ * the next one, so rapid navigation never leaves the stage covered. Order under a curtain: cover → sail →
+ * landing → horizon on the frieze's ground line → lift (a landing drop lifts through the doorway).
  */
 export function createController(opts: {
   store: Store;
@@ -47,6 +55,8 @@ export function createController(opts: {
   let queue: Promise<void> = Promise.resolve();
   let timer: ReturnType<typeof setTimeout> | null = null;
   const playListeners: ((p: boolean) => void)[] = [];
+  const landingListeners: ((l: LandingId | null) => void)[] = [];
+  const setLanded = (l: LandingId | null) => { landed = l; landingListeners.forEach((fn) => fn(l)); };
 
   const ribbons = () => {
     const s = store.get();
@@ -68,18 +78,20 @@ export function createController(opts: {
     if (world) {
       if (landed && landed !== landing) {
         await world.setLanding(null);
-        landed = null;
+        setLanded(null);
       }
       await world.sailTo(to, { instant: kind !== "sail" });
     }
     if (my !== gen) return;
-    if (curtainDown) {
-      await curtain.lift();
-      curtainDown = false;
-    }
     if (world && landing !== landed) {
       await world.setLanding(landing);
-      landed = landing;
+      setLanded(landing);
+    }
+    if (my !== gen) return;
+    if (curtainDown) {
+      world?.horizonFromFrieze(curtain.groundY());
+      await curtain.lift();
+      curtainDown = false;
     }
     settled = to;
     ribbons();
@@ -118,7 +130,7 @@ export function createController(opts: {
     const first = songById(settled)!;
     running++;
     queue = world.sailTo(settled, { instant: true })
-      .then(async () => { if (first.landing) { await world.setLanding(first.landing); landed = first.landing; } ribbons(); })
+      .then(async () => { if (first.landing) { await world.setLanding(first.landing); setLanded(first.landing); } ribbons(); })
       .catch((e) => console.error(e))
       .finally(() => { running--; });
   }
@@ -130,5 +142,13 @@ export function createController(opts: {
     stop() { setPlaying(false); },
     playing: () => playingNow,
     onPlayingChange(fn) { playListeners.push(fn); },
+    landing: () => landed,
+    leaveLanding() {
+      if (!world || !landed) return Promise.resolve();
+      const done = queue.then(async () => { await world.setLanding(null); setLanded(null); });
+      queue = done.catch((e) => console.error(e));
+      return done;
+    },
+    onLandingChange(fn) { landingListeners.push(fn); },
   };
 }