feat(traps): activation VFX/SFX, explosion effect, and help section

Wire mimic/pit/arrow/laser media on activate, poison/explosion via effects, and document the scene editor and traps in Instructions.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/shared/types/effects.ts

@@ -7,6 +7,7 @@ export type EffectToolType =
   | 'lightning'
   | 'sunbeam'
   | 'poisonCloud'
+  | 'explosion'
   | 'freeze'
   | 'exploreBrush'
   | 'eraser';
@@ -20,6 +21,7 @@ export type EffectInstanceType =
   | 'lightning'
   | 'sunbeam'
   | 'poisonCloud'
+  | 'explosion'
   | 'freeze'
   | 'scorch'
   | 'ice'
@@ -104,6 +106,15 @@ export type PoisonCloudInstance = EffectInstanceBase & {
   lifetimeMs: number;
 };
 
+/** «Взрыв» — one-shot webm в точке удара (тот же ассет, что у ловушки). */
+export type ExplosionInstance = EffectInstanceBase & {
+  type: 'explosion';
+  at: { x: number; y: number };
+  radiusN: number;
+  intensity: number;
+  lifetimeMs: number;
+};
+
 export type FreezeInstance = EffectInstanceBase & {
   type: 'freeze';
   at: { x: number; y: number };
@@ -148,6 +159,7 @@ export type EffectInstance =
   | LightningInstance
   | SunbeamInstance
   | PoisonCloudInstance
+  | ExplosionInstance
   | FreezeInstance
   | ScorchInstance
   | IceInstance