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/npc.dialog-shop.md

@@ -101,3 +101,7 @@
 ## Status
 
 `PARTIAL`。NPC 点击、基础对话承接、普通/扩展商店协议骨架、购买出售 UI 和个人商店字段已经存在，但当前端仍有明确的多 tab 更新索引错误、购买模式错误放行出售、个人商店招牌不可点击打开、自己商店状态不分支、native 动作门控缺失以及本地硬编码库存/金币旁路。已完成审计并记录，未修改实现代码。
+
+### 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：`npc_shop_system.gd`, `private_shop_system.gd`, `test_npc_shop_parity.gd`, `test_private_shop_bundle_parity.gd`。