Add shared core attribute allocation

docs/STAT_LEVEL_SCALING.md

@@ -150,6 +150,19 @@ targetRaw =
   / weaponMultiplier(referenceLevel)
 ```
 
+SHD.build stores the reference level associated with each weapon-tier range.
+Builder calculations use that recorded observation level in the ratio above.
+The curve's level-1 origin does not imply that every stored range was observed
+at level 1. T2 availability limits likewise do not change a range's recorded
+reference level.
+
+Firepower, Toughness, and Engineering nominal tier ranges are stored once in
+the shared core-allocation configuration at reference level 50. Scale those
+nominal endpoints to the target level using the appropriate equipment-family
+multiplier, then derive the combined pool bounds by multiplying each endpoint
+by three. Redistribution changes the split between the three cores without
+changing the selected item's total allocation.
+
 The `1.14` offset is provisional and is currently validated only for the
 level-40-to-level-50 interval. Preserve enough decimal precision to revise it
 without migrating rounded data.
@@ -217,4 +230,3 @@ Useful known outputs include:
   `2187 DMG`, `139 FP`, `142 TGH`, `36 ENG`.
 - Weapon sample: level 40 `753 DMG`, `44 FP`, `15 TGH`, `45 ENG`; level 50
   `873 DMG`, `51 FP`, `18 TGH`, `52 ENG`.
-