feat(play): always generate new scene for freeform text input + enhance insert-beat

User feedback: custom interactions rarely produce new story content because
the classifier heavily biased toward insert-beat (single reaction, no scene
change). Three changes to fix this:

1. Freeform text input now always triggers a full scene generation (skips
   the classify step entirely) — users who type expect the story to advance.

2. Vision (background click) classifier de-biased: prompt now favors
   change-scene when uncertain, and the code fallback flipped from
   insert-beat to change-scene. insert-beat narrowed to pure observation.

3. Insert-beat enhanced: generates 1-3 beats (was 1) with follow-up
   choices (was: loop back to original beat). Even when vision classifies
   as insert-beat, the player gets richer content and new options.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/types/index.ts

@@ -695,8 +695,19 @@ export type InsertBeatPartial = {
   lineDelivery?: string;
 };
 
+/** Multi-beat response: 1-3 beats + optional follow-up choices. */
+export type InsertBeatMulti = {
+  beats: InsertBeatPartial[];
+  /** Follow-up choices shown after the last beat (max 2). */
+  choices?: { label: string; effect: string }[];
+};
+
 export type InsertBeatResponse = {
   partial: InsertBeatPartial;
+  /** Additional beats beyond the first (for richer insert-beat interactions). */
+  extraBeats?: InsertBeatPartial[];
+  /** Follow-up choices shown after the last inserted beat. */
+  followUpChoices?: { label: string; effect: string }[];
   characters: Character[];
 };