fix: resolve circular dependency in discipline-slice → discipline-effects

Replaced computeDisciplineEffects() import in discipline-slice.ts with
inline XP bonus calculation using calculateStatBonus from discipline-math.
This avoids the circular chain: discipline-effects → discipline-slice → discipline-effects.

docs/dependency-graph.json

@@ -1,6 +1,6 @@
 {
   "_meta": {
-    "generated": "2026-05-27T19:08:44.608Z",
+    "generated": "2026-05-28T07:32:46.775Z",
     "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."
   },
@@ -326,7 +326,6 @@
       "data/equipment/feet.ts",
       "data/equipment/hands.ts",
       "data/equipment/head.ts",
-      "data/equipment/shields.ts",
       "data/equipment/swords.ts"
     ],
     "data/equipment/feet.ts": [
@@ -347,7 +346,6 @@
       "data/equipment/feet.ts",
       "data/equipment/hands.ts",
       "data/equipment/head.ts",
-      "data/equipment/shields.ts",
       "data/equipment/swords.ts",
       "data/equipment/types.ts",
       "data/equipment/utils.ts"
@@ -530,6 +528,7 @@
       "data/disciplines/enchanter.ts",
       "data/disciplines/fabricator.ts",
       "data/disciplines/invoker.ts",
+      "effects/discipline-effects.ts",
       "types.ts",
       "types/disciplines.ts",
       "utils/discipline-math.ts",