chore: delete 106 unreachable *_system.gd and their parity tests

These files were loaded only by their own test_*_parity.gd and never by
the runtime (transitively checked, incl. client_phase_integration_system).
Removes 76 manifest implementation/evidence references across 18
contracts; contract docs get a note that conclusions based on them are
void. Live systems kept: chest, consumable, item_attr, metin_socket,
whisper_chat.

Full headless suite: no new failures (7 failing + 5 headless-hanging
render tests are identical before the deletion).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

audit/contracts/world.environment-weather.md

@@ -102,3 +102,7 @@
 ## 下一轮验证入口
 
 - 进入实现阶段后，优先修复正式 GameScene 的天气/地图环境接入和 fog/filter/lens flare/wind 中的已确认 GAP；修复后重新运行本合同四组测试并增加真实渲染证据。
+
+### 2026-09-22 死代码删除
+
+以下文件只被自身测试引用、运行时从不加载，已删除；本文中以它们为实现或证据的结论作废，相关行为需按 40250 源码单元重新移植：`test_weather_daynight_parity.gd`, `weather_daynight_system.gd`。