docs(skills): objectstack-formula eval case 4 names the refused date forms without spelling its own must_not_contain strings (#26978)

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Fixes #26814

Clause-②: no
Metadata-protocol: none

## 维护者速读

- 改了什么:`skills/objectstack-formula/evals/cel-predicates-formulas.json` 第
4 例的参考答案改写——不再把自己 `must_not_contain` 要拒的两个字符串(JS 的 Date 构造、`today()`
加数字)原样拼出来,改为点名其形态;七个断言、全部事实一字不少,文件字节数不变(5407 B),token 棘轮行不动;附
`@objectstack/skills` patch changeset。
- 为什么改:参考答案自己含被拒字符串,按该例标准作答反而判错(总监复审 PR #26810 发现)。
- 风险与回滚:只改一条 JSON 字符串与一个 changeset,无 schema/行为变化;回滚即 revert 本 PR。
- 先看:`skills/objectstack-formula/evals/cel-predicates-formulas.json`(第 4
例 `expected_output` 一行)。
- 两分钟验证:`node scripts/check-skills-token-ratchet.mjs`,预期看到该文件 `1352
tokens (ceiling 1352; headroom 0)` 且总判定 ✓。
- 需要你做的:批准本 PR(`skills/**` 受管面,Tier H,保持 draft 等 GOVERNED_APPROVERS
批准;席位不 ready/不入队)。

## What changes

- **Case 4 `expected_output`** of
`skills/objectstack-formula/evals/cel-predicates-formulas.json` no
longer spells its own `must_not_contain` strings. The two phrases that
carried them are reworded; everything else in the case is
byte-identical:
- "never `new Date()` / `Date.now()`" → "never a JS `Date` /
`Date.now()`"
- "never `today() + 45` (date arithmetic faults)" → "never date
arithmetic on `today()` (it faults)"
- **Every assertion and fact kept**: the CEL-envelope seed `close_date:
cel`daysFromNow(45)``, the determinism gate (two `os build` runs
byte-identical), `daysBetween(today(), record.close_date)`, the
`record.close_date - today()` duration-stored-as-`{}` trap, and the
date-arithmetic fault. `must_contain` / `must_not_contain` are
untouched.
- **Changeset**
`.changeset/26814-formula-eval-case4-self-consistent.md`,
`@objectstack/skills` patch (the evals ship in the published catalog).
- No forced test edits. No ratchet row moves.

## Why

Case 4 refused `new Date(` and `today() + ` in an answer while its own
reference answer contained both, so an answer that matched the reference
was graded wrong. Found by the contract review of PR #26810 (card
#26814).

## Tests

Per-case cross-check over the file (each case: no `must_not_contain`
string inside its own `expected_output`, every `must_contain` string
present), at `origin/main` 912076f and at this head:

```text
origin/main 912076f:  case 4: must_not_contain "new Date(" PRESENT
                       case 4: must_not_contain "today() + " PRESENT
                       cases=7 failures=2
head f853185:         cases=7 failures=0
```

`JSON.parse` of the file succeeds at this head.

### Skills readings (`skills/**` diff — whole-file and whole-package,
before → after)

| Reading | before (912076f) | after (f853185) |
|:---|---:|---:|
| `evals/cel-predicates-formulas.json` lines / bytes / tokens | 75 /
5407 / 1352 | 75 / 5407 / 1352 |
| whole package, all `skills/*/SKILL.md` lines / bytes | 4605 / 224961 |
4605 / 224961 |
| whole package, all `skills/*/evals/*.json` lines / bytes | 1479 /
94793 | 1479 / 94793 |

Token = `ceil(bytes / 4)`, the convention
`scripts/check-skills-token-ratchet.mjs` declares. Ceiling row for the
file stays at 1352 (headroom 0, unchanged).

## Acceptance notes

- Same-byte rewrite achieved, so the standing ruling 「A:先削重复,余额按实测提高」
was not needed and the ratchet row did not move.
- The cross-check script is a local probe (not committed); its two rules
are the ones the card's acceptance line states.

## Verification

Local gate subset at head f853185 (`node scripts/pm/dispatch-gates.mjs
--commands --repo objectstack-ai/objectstack`, no paths; 42 derived
commands run serially, each exit code captured before any pipe):

<details><summary>42 / 42 exit 0 · `--ran` reconciliation: 42 derived,
42 run, 0 NOT-MEASURED, 0 UNRUN</summary>

```text
✓ check-skills-token-ratchet: skills/objectstack-formula/evals/cel-predicates-formulas.json is 1352 tokens (ceiling 1352; headroom 0).
✓ check-skills-token-ratchet: 82 authored bundle file(s) within their ceilings; 10 generator-owned file(s) measured, not ratcheted.
Run reconciliation — 42 derived, 42 run, 0 NOT-MEASURED, 0 UNRUN.
✓ dispatch-gates --ran: 42 derived famil(ies) accounted for — 42 run, 0 NOT-MEASURED (a DERIVED zero — all 42 recorded an exit code and none of them is 3).
```

Build closure first: `bash scripts/pm/os-verify-lock.sh -c 'pnpm build
--concurrency=2'` → `VERDICT command-exit 0 · held the lock 841s
(14m01s)`.

</details>

Every family CI runs on the PR (`Lint & Repo Gates`, `TypeScript Type
Check`, `Check Changeset`, `Governed Surface Queue Guard`, …) is read
from this PR's check-runs, not re-run locally. `test:repo` is not in the
local subset (it is CI's; this diff edits no test). Dogfood battery: n/a
(no `!` in the title, no `(narrowing)` arm).


---
_Generated by [Claude
Code](https://claude.ai/code/session_01ADHkmPQ8p3cVKear7Mchi2)_

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

Author: objectstack-fleet[bot]

.changeset/26814-formula-eval-case4-self-consistent.md

@@ -0,0 +1,12 @@
+---
+'@objectstack/skills': patch
+---
+
+docs(skills): objectstack-formula eval case 4's reference answer names the refused date forms without spelling its own `must_not_contain` strings
+
+Clause-②: no
+Metadata-protocol: none
+
+- **Before.** Case 4 of `skills/objectstack-formula/evals/cel-predicates-formulas.json` refuses `new Date(` and `today() + ` in an answer, yet its own `expected_output` spelled both (`` `new Date()` `` and `` `today() + 45` ``), so a reference-grade answer was graded wrong.
+- **Now.** The reference answer says "never a JS `Date` / `Date.now()`" and "never date arithmetic on `today()` (it faults)", as case 7 names "the `label` macro". Every assertion and every fact stays: the CEL envelope seed, the determinism gate, `daysBetween(today(), record.close_date)`, the `{}` duration trap. A per-case cross-check (no `must_not_contain` string inside its own `expected_output`, every `must_contain` string present) reports 0 failures over all 7 cases; the file keeps its byte size, so its token-ratchet row does not move.
+- No schema, key or behaviour changes.

skills/objectstack-formula/evals/cel-predicates-formulas.json

@@ -34,7 +34,7 @@
     {
       "id": 4,
       "prompt": "Demo opportunities should close 45 days after the package is installed, and a formula should show how many days remain until close.",
-      "expected_output": "Seed value as a CEL envelope, `close_date: cel`daysFromNow(45)``, never `new Date()` / `Date.now()` (the determinism gate: two `os build` runs must be byte-identical). Days remaining is `daysBetween(today(), record.close_date)` — never `record.close_date - today()` (a duration stored as `{}`) and never `today() + 45` (date arithmetic faults).",
+      "expected_output": "Seed value as a CEL envelope, `close_date: cel`daysFromNow(45)``, never a JS `Date` / `Date.now()` (the determinism gate: two `os build` runs must be byte-identical). Days remaining is `daysBetween(today(), record.close_date)` — never `record.close_date - today()` (a duration stored as `{}`) and never date arithmetic on `today()` (it faults).",
       "files": [],
       "assertions": {
         "must_contain": ["cel`", "daysFromNow(", "daysBetween("],