Rename ship/station scrap drop entities to "debris"

src/lib/sim/ThreatCostCalculator.cpp

@@ -66,7 +66,7 @@ ThreatCostTable computeThreatCostTable(const GameConfig& config)
     ThreatCostTable table;
 
     // Scrap threat (REQ-THREAT-SCRAP) is the constant inverse of the scrap-drop
-    // conversion (REQ-RES-SCRAP-DROP): one scrap is worth 1 / scrap_per_threat.
+    // conversion (REQ-RES-DEBRIS-DROP): one scrap is worth 1 / scrap_per_threat.
     // Set it up front so reprocessing-only item threats (below) can use it, and so
     // it no longer depends on any ship's threat cost.
     table.scrapThreat = config.world.scrapPerThreat > 0.0