docs: name combo hang-stop from comboPredicates.ts

[HouMinXi]

Related to #14004. The tracker already closed after 7cc454d93 went release-green.

#14022 landed the STRIP documentation and the DOC_ONLY_ALLOWLIST entry for COMBO_LOOP_SAFETY_TIMEOUT_MS. Rebased onto that tip; the STRIP overlap is gone.

What is left:

• ENVIRONMENT.md no longer backticks the hang-stop constant as an env name. It points at comboPredicates.ts instead. The allowlist already keeps the checker green; this is the prose form of the same fact.
• changelog fragment for that sentence.

node scripts/check/check-env-doc-sync.mjs on this tree: 613 / 825 / 842, all three directions none, exit 0.

⚠️ base-red inherited: #13866

[HouMinXi]

This PR documents both gaps that make check-env-doc-sync red on current release/v3.8.51:

1. OMNIROUTE_STRIP_SYSTEM_PREAMBLE is a real process.env read (openai-to-claude.ts) missing from .env.example / ENVIRONMENT.md. Same fix as fix(ci): document OMNIROUTE_STRIP_SYSTEM_PREAMBLE — the env/docs base red blocking every PR #14022, but this branch is on current tip (0 behind). fix(ci): document OMNIROUTE_STRIP_SYSTEM_PREAMBLE — the env/docs base red blocking every PR #14022 is 14 behind and only covers this key.
2. COMBO_LOOP_SAFETY_TIMEOUT_MS is a hardcoded constant in comboPredicates.ts. Backticks in ENVIRONMENT.md made the checker treat it as an env var. fix(ci): document OMNIROUTE_STRIP_SYSTEM_PREAMBLE — the env/docs base red blocking every PR #14022 does not touch that. Merging fix(ci): document OMNIROUTE_STRIP_SYSTEM_PREAMBLE — the env/docs base red blocking every PR #14022 onto current tip still leaves the contract red.

If #14022 lands first, this PR rebases and drops the STRIP overlap, keeping only the constant prose change.

[HouMinXi]

#14004 closed itself after release/v3.8.51 went green at 7cc454d93 (run 35338595127).

#14022 is already on that tip. It documents OMNIROUTE_STRIP_SYSTEM_PREAMBLE and allowlists COMBO_LOOP_SAFETY_TIMEOUT_MS in DOC_ONLY_ALLOWLIST. I re-ran node scripts/check/check-env-doc-sync.mjs on 7cc454d931:

Code references:          613 unique vars
In .env.example:          825 unique vars
In docs/reference/ENVIRONMENT.md: 843 unique vars
  ✓ In code but missing from .env.example: none
  ✓ In .env.example but missing from ENVIRONMENT.md: none
  ✓ In ENVIRONMENT.md but missing from .env.example: none
✓ Env / docs contract is in sync.

This PR's leftover vs current tip is the STRIP overlap plus a prose rewrite of the hang-stop sentence. The allowlist already covers that name, so the rewrite is unused. Closing as superseded by #14022.

Related to #14004. The issue is already closed.

[HouMinXi]

Reopened. I closed this by mistake; that call is the maintainer's.

#14022 already landed on 7cc454d93 and the env/docs checker is green there (DOC_ONLY_ALLOWLIST covers COMBO_LOOP_SAFETY_TIMEOUT_MS). This branch still has the STRIP overlap plus a prose rewrite of the hang-stop sentence. Leaving the PR open for you to drop or retarget.

[HouMinXi]

Rebased onto 7cc454d93 (#14022 already on that tip).

STRIP documentation is already on the branch. The remaining unique diff is the ENVIRONMENT.md sentence that still backticks COMBO_LOOP_SAFETY_TIMEOUT_MS as if it were an env var, plus a changelog fragment for that sentence. The allowlist already keeps check-env-doc-sync green; this is the prose form of the same fact.

Local node scripts/check/check-env-doc-sync.mjs on this tree: 613 / 825 / 842, all three directions none, exit 0.

#14004 stays with whoever owns the tracker.

[HouMinXi]

Rebased onto current release/v3.8.51 (36493a6270). Unique commits unchanged.

[diegosouzapw]

Thanks @HouMinXi — merging via the release merge-train. Validated in local merge-train (mt-train10c) on the devbox @ train tip 4d841aa1c740bbaa03868dc0a403c62099a99a42 with the 72 sibling PRs of this batch: typecheck:core, file-size, complexity, cognitive-complexity, changelog-integrity green; changed-area node:test 831/831 (0 failing) and vitest 480/482 — the two reds are autoCombo/provider-family-combos.test.ts timing out at 20s, which reproduces on the PURE release tip under the full vitest suite (and is already tracked by the Release-Green issue #13866), so it is inherited, not this batch's. Merged --admin per merge-gates §3/§4/§7.