docs(agents): name the missing tool, not an absent sibling scripts/pm/ (#17375)

The gate-derivation rules in `.claude/agents/os-dev.md` stated that sibling
repos have no `scripts/pm/`. Measured on objectui `origin/main` (`a646262`):
`scripts/pm/check-half-states.mjs` is there, with a live standing caller
(`.github/workflows/half-state-patrol.yml`); only `dispatch-gates.mjs` is
absent (control, same tree, same channel). The operative half is unchanged —
a sibling without `dispatch-gates.mjs` still derives its gate families by
hand from its own `package.json` and `.github/workflows/`.

Rewritten in place, net-zero (403 lines before and after), 71 -> 114 bytes,
under the 120-byte line cap. The sentence no longer claims anything about
cloud, which is attached to no seat here and was never measured.

Claude-Session: https://claude.ai/code/session_01YKEjmbYNvYWJvWGSWx26zK

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-litant

.claude/agents/os-dev.md

@@ -146,7 +146,7 @@ model: opus
 - 派生答哪些门禁读你改的文件,不答哪些测试测这个脚本。
 - 跑同目录点名它的 `*.test.ts`,加同包 tests 下 `git grep` 该脚本文件名的全部命中。
 - 该脚本只住在 objectstack,答案只关于它所在的树:每次推导第一行(stderr)点名仓与 commit。
-- 读之前先核对;姊妹仓(objectui / cloud)没有 `scripts/pm/`。
+- 读之前先核对;姊妹仓未必有 `scripts/pm/dispatch-gates.mjs`:objectui 只有 `check-half-states.mjs`。
 - 把它们的路径喂进 objectstack 检出,得到的是 objectstack 的门禁族:形态完整、退出 0、全错。
 - 那边的清单从该仓自己的 `package.json` 与 `.github/workflows/` 手工推导。
 - 加 `--repo <owner>/<name>` 申报本次答案该属于哪个仓,不匹配即拒绝并同时点名两个仓。