feat(costs): Add source for Obsidian Chitin Tails

Due to the amount of variables at play, the actual cost may be slightly
higher with poor luck. This will be adjusted if it becomes an issue.

bonemarketsolver/data/costs.py

@@ -140,8 +140,9 @@ class Cost(Enum):
     NEVERCOLD_BRASS = 1
 
     # Obsidian Chitin Tail
-    # No consistent source
-    OBSIDIAN_TAIL = cp_model.INT32_MAX/2
+    # Heist, Osteology Wing, 5 at a time
+    # 4 actions for Casing, 6 actions for heist
+    OBSIDIAN_TAIL = (10*ACTION)/5
 
     # Parabolan Orange-apple
     # Parabolan Base-camp, electricity and hedonism, 2 at a time