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/main/effects/effectsStore.test.ts

@@ -82,3 +82,22 @@ void test('pruneExpired: яд удаляется после lifetime', () => {
   assert.equal(store.pruneExpired(), true);
   assert.equal(store.getState().instances.length, 0);
 });
+
+void test('pruneExpired: взрыв удаляется после lifetime', () => {
+  const store = new EffectsStore();
+  store.dispatch({
+    kind: 'instance.add',
+    instance: {
+      id: 'ex_test',
+      type: 'explosion',
+      seed: 1,
+      createdAtMs: Date.now() - 20_000,
+      at: { x: 0.5, y: 0.5 },
+      radiusN: 0.08,
+      intensity: 1,
+      lifetimeMs: 4200,
+    },
+  });
+  assert.equal(store.pruneExpired(), true);
+  assert.equal(store.getState().instances.length, 0);
+});

app/main/effects/effectsStore.ts

@@ -52,6 +52,7 @@ export class EffectsStore {
         i.type === 'lightning' ||
         i.type === 'sunbeam' ||
         i.type === 'poisonCloud' ||
+        i.type === 'explosion' ||
         i.type === 'darkness'
       ) {
         return now - i.createdAtMs < i.lifetimeMs;