fix: deduct component consumption from element pools in mana conversion

Bug #293: elementDrain was computed but never subtracted from element pools.
The tick pipeline now applies net regen (produced - drained) instead of
gross production to element pools, matching the spec §8 regen deduction model.

docs/dependency-graph.json

@@ -1,6 +1,6 @@
 {
   "_meta": {
-    "generated": "2026-06-08T09:39:57.039Z",
+    "generated": "2026-06-08T09:52:20.951Z",
     "description": "Import dependency graph for src/lib/game. Keys are files, values are arrays of files they import.",
     "usage": "To find what a file affects, search for its path in the VALUES. To find what a file depends on, look at its KEY entry."
   },