test: add cross-module integration tests for tick pipeline

Add 38 integration tests split across 4 files (all under 400 lines):
- cross-module-helpers.ts: shared resetAllStores() and tickN() utilities
- cross-module-combat-meditation.test.ts (12 tests): combat floor
  clearing, meditation regen flow, incursion effects, convert action
- cross-module-prestige-discipline.test.ts (15 tests): prestige loop
  reset, discipline mana drain/XP, pact ritual completion
- cross-module-lifecycle-consistency.test.ts (11 tests): full loop
  lifecycle, store consistency invariants, pause/gameOver blocking

All 38 new + 112 existing tests pass.

docs/dependency-graph.json

@@ -1,6 +1,6 @@
 {
   "_meta": {
-    "generated": "2026-05-25T13:20:05.764Z",
+    "generated": "2026-05-25T15:37:16.139Z",
     "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."
   },