Add cross timeline interaction gym

docs/gyms/cross-timeline-interactions/gym_pattern5_choice_jump.dtl

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+# ============================================================
+# Pattern 5: Choice Routes to Different Timelines
+# ============================================================
+# Each choice branch doesn't just set a variable —
+# it JUMPS to a completely different timeline.
+# ============================================================
+
+label start
+
+join Miko center
+join Advisor right
+
+Advisor (doubt): This is a crossroads. Each choice leads to a different\
+destination.
+
+Miko (neutral): Where should we go?
+
+- The sunny meadow
+    Miko (joy): I love flowers! Let's go to the meadow.
+    Advisor (pl5): Fresh air will do us good.
+    jump gym_main/menu
+
+- The dark cave
+    Miko (doubt): It's so dark in there... but I'm curious.
+    Advisor (doubt): Bring a torch. We don't know what lurks inside.
+    jump gym_main/menu
+
+- Back to the hub
+    Miko (smile): Good idea. I've seen enough crossroads.
+    Advisor (pl5): A safe choice.
+    jump gym_main/menu
+
+# Note: In a real game, these would jump to:
+#   jump meadow_scene/start
+#   jump cave_scene/start
+#   jump hub_scene/main
+# But here we just return to the hub for the demo.