feat(foreshadow): 写章上下文注入到期/逾期伏笔 + AI 顺势回收指令

- assemble 富渲染伏笔行：补『期望回收 X-Y章』+『（已逾期！）』标记（仍在 volatile 缓存段，守不变量 #9）
- 新增 foreshadow_inject 纯函数：除大纲显式窗口外，按当前章自动纳入
  『回收窗口内 / 已逾期且未 CLOSED』的伏笔（确定性、无向量，守不变量 #6）
- write_craft.md 增克制指令『到点顺势收，别为收而收』；foreshadow.md 描述对齐新注入格式
- MemoryRepos 加可选 foreshadow_ledger（照 review 先例，None 优雅降级）
- 金标准仅 foreshadow spec hash 变更；后端全绿 pytest 1032 passed

packages/agents/tests/fixtures/prompt_hashes.json

@@ -11,7 +11,7 @@
   "de-ai": "9ce3020cdd4b223cc4d13c289babd2811bbfece4b392711dcba4fd0301c87249",
   "expand": "74a5d71c4ffc11b78bf80c7ab3fc3eebfc1192ffff2b0bfa9957ec2c33d9d05e",
   "fine-outline": "0ae0b71f4144e82ffa2a7a0059505525857f7d9797e94ced25da3129355a46ed",
-  "foreshadow": "405696461fef445e4609227c40df6c4812737735edea7e1966ee84afe7635645",
+  "foreshadow": "b3f80c86d5f410ac4abe1fbfcacf0ad3c8ef547a0082cb0ea7a63b2edf5f6f24",
   "glossary": "54e95d21d10b9209287c10517134f485ca5ce4a3ef08291aac954dcf492d73d0",
   "golden-finger": "416e8591d99ea1296db550bc428012aa937eed47eea03ef435e92c6843005e21",
   "name": "ee759bc967773e3300813f250f233c872fd3a4f0cb00086509ffc3552d67700b",