docs(pm-skill): the footer-synthesis mechanism is measured false — replace the untested row with the reading

The row proposed a mechanism for the attribution-footer variation and marked it
未实测 with an explicit refusal to compress the observation into a law: the tool
synthesises a footer only for a body that carries none.

Measured twice now, on two different PRs, in the direction that mechanism
predicts: a body edit sent through the MCP `update_pull_request` wrapper with no
footer of its own reads back, through the same channel, with NO footer at all —
no synthesised block, nothing appended. The mechanism is false, so the row that
proposed it is replaced BY the reading, at the same line count. The neighbouring
rows are untouched, including the one that refuses to generalise any single form
across channels and actions, which still governs this line.

⚠️ This disagrees with `AGENTS.md`'s edit-side reading (session-URL footer
survives, the platform appends a bare block). AGENTS.md is outside this flight's
file surface; the conflict is reported rather than silently resolved.

Ceiling unchanged at 395: this correction is line-neutral and buys nothing.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018dxq7YqsLDMeZDZ5AzsgJX

Author: claude[bot]

.claude/skills/pm-dispatch/references/platform-readings.md

@@ -301,7 +301,7 @@
 - MCP `update_pull_request` 包装器删掉 PR 正文的页脚块。
 - 裸 REST `PATCH /pulls` 追加一个裸页脚并保留既有 session-URL 页脚,差恰 58 字节。
 - 同一 MCP 包装器上有反例:把已带页脚的正文整体重送,两条页脚均逐字节存活。
-- 提出的机理是工具只为无页脚的正文合成页脚 —— ⛔ 未实测,⛔ 不把观察压成定律。
+- 送无页脚正文经 MCP 编辑回读仍无页脚(两次实测)⇒ 它不为无页脚正文合成页脚。
 - 第四形:裸 REST `POST /pulls` 建 PR 时,在已带 session-URL 页脚的正文后再追加一条同形页脚。
 - 该追加带前置横线、恰 90 字节,送出体是存储体的严格前缀。
 - ⇒ 追加形态随通道与动作(建 / 改)变,⛔ 不由任一条推其余;写后必回读。