docs(pm): label writes re-read current labels in the same action — stale snapshots are invalid snapshots (#9226)

[os-zhuang]

Fixes#9226

Main deliverable — references/platform-readings.md (in-place, line-neutral)

The issue_write labels whole-set-replace trap line is rewritten in place (no new lines). Core increment per the card: 写标签前同一动作内重读现值合并 —— 隔轮/隔小时的旧读数视为无效快照. All pre-existing elements are preserved: whole-set replace (not append), the silent-stripping consequence, true append via REST POST /issues/{n}/labels, and the post-write read-back. Rationale (from the card): the old wording pinned read-then-union but not the freshness of the read — a reading taken early in a round plus a write 80 minutes later satisfied it literally while bypassing it semantically; post-write read-back cannot catch this class, so the only effective defense is compressing the read-write window to seconds.

Piggyback (scope-addendum comment on #9226) — landed, not dropped

SKILL.md review section (the skill-surface ACCEPT 三件套, item ①) now states that the review seat for clause-① skill-surface PRs must itself run at the contract-review tier, referenced via the dispatch-gates constant CONTRACT_REVIEW_TIER — no model name written, single source preserved. Funded line-neutrally by extending the existing line (long-line precedent in the file: lines up to 492 chars); no re-wrap, no new line.

Line budget (ratchet, read on the spot)

file	before	after	ceiling
.claude/skills/pm-dispatch/references/platform-readings.md	133	133	134
.claude/skills/pm-dispatch/SKILL.md	682	682	682

Tier derivation (verbatim, node scripts/pm/dispatch-gates.mjs --tier on the changed paths)

Model tier — MANDATORY: claude-fable-5 (derived from the file surface, not recalled).
- .claude/skills/pm-dispatch/SKILL.md ⇢ '.claude/skills/pm-dispatch/**' — clause ① of the model-tiering ruling: a card editing the PM dispatch skill is fable-mandatory, references included — the skill is the lane's own operating protocol and a wrong edit propagates to every later dispatch
- .claude/skills/pm-dispatch/references/platform-readings.md ⇢ '.claude/skills/pm-dispatch/**' — clause ① of the model-tiering ruling: a card editing the PM dispatch skill is fable-mandatory, references included — the skill is the lane's own operating protocol and a wrong edit propagates to every later dispatch
The only exit is the measured quota exemption (fable unavailable ⇒ opus, never lower), recorded with its reason in the claim comment's `Container & model` line.
Clause ② is NOT reachable from paths: a card that changes contract accept/reject behaviour or widens the public surface is fable-mandatory too, judged from the card CONTENT. This line is a FLOOR, never a clearance.

Verification — gate union re-run after the final commit, at 0627eed38

doc-authoring: PASS
doc-formula-expressions: PASS
pm-skill-id-lint: PASS
pm-skill-ratchet: PASS
skill-frame-sync: PASS
nul-bytes: PASS
union at HEAD: 0627eed38

Gate families re-derived from the actual changed paths (node scripts/pm/dispatch-gates.mjs on the two files): the five families above, matching the dispatch expectation; no additions beyond the derived set. .claude/-only change — releases nothing; skip-changeset applied.

This is a skill-surface PR (.claude/skills/**): draft, awaiting a human merge — never ready/queue/auto-merge.

---

Generated by Claude Code