Prevent poisoned ROADMAP ids before allocation (#3116)

Constraint: roadmap-next-id.sh must preserve single-id stdout on success while failing closed if duplicate validation cannot run.
Rejected: Relying only on CI/pre-push duplicate checks | the helper is used immediately before appending and must not certify an already-poisoned file.
Confidence: high
Scope-risk: narrow
Directive: Keep roadmap-next-id.sh stdout machine-clean; route validation failures and checker availability errors to stderr, and keep focused helper behavior coverage in the docs/ROADMAP CI path.
Tested: scripts/roadmap-next-id.sh ROADMAP.md printed 725 before appending #725 and 726 after; temp ROADMAP with duplicate 999 exited nonzero and listed duplicate id; scripts/roadmap-check-ids.sh ROADMAP.md; bash -n scripts/roadmap-next-id.sh scripts/roadmap-check-ids.sh; python -m unittest discover -s tests -p test_roadmap_helpers.py; python -m pytest tests/test_roadmap_helpers.py -q; SKIP_CLAW_PRE_PUSH_BUILD=1 bash .github/hooks/pre-push
Not-tested: full cargo workspace build, unchanged docs/script-only path

ROADMAP.md

@@ -7615,3 +7615,5 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 723. **Concurrent dogfood claws allocate ROADMAP ids manually and collide — same id reused by two contributors simultaneously, causing PR ROADMAP.md conflicts and lost entries** — observed live 2026-05-26 during Jobdori+Gaebal parallel dogfood session: Gaebal filed stale-local-probe as #719; Jobdori landed `plugins list <filter>` as #719 on main first; Gaebal shifted to #720; Jobdori landed `claw help <topic>` as #720; stale-local-probe eventually landed as #721 after two forced rebase cycles. The ROADMAP append workflow has no reservation or conflict-aware id allocation. **Required fix shape:** (a) add `scripts/roadmap-next-id.sh` that reads the highest id from ROADMAP.md and prints `highest+1` — claws should call this immediately before appending any new entry; (b) document in CONTRIBUTING.md that id allocation is optimistic-append: call `roadmap-next-id.sh` immediately before the append, git-pull first, resolve collisions at push time by re-numbering the appended entry; (c) long-term: a GitHub Action that validates no duplicate ROADMAP ids on PR would catch this before merge. Added `scripts/roadmap-next-id.sh` (this commit). Source: Gaebal Gajae live observation, 2026-05-26.
 
 724. **DONE — ROADMAP duplicate-id validation guard for helper-era append collisions** — follow-up to #723 after dogfood showed `scripts/roadmap-next-id.sh` still printed 724 and exited 0 when a temp ROADMAP copy already contained a second `723. ...` line. This PR closes the gap for new optimistic-append collisions by adding `scripts/roadmap-check-ids.sh`, wiring it into docs CI and the local pre-push hook, documenting the pre-push command in CONTRIBUTING, and mentioning the guard from `roadmap-next-id.sh`. The guard defaults to ids >=723 so current historical roadmap content and old numbered lists do not block docs-only PRs; `--min-id 1` is available for a strict whole-file audit once legacy collisions are cleaned up. **Verification:** `scripts/roadmap-check-ids.sh` passes on current ROADMAP; a temp copy with an appended duplicate `723.` fails nonzero and lists duplicate id 723 with line numbers. Source: Jobdori dogfood follow-up on origin/main `922c2398`, 2026-05-25. [SCOPE: docs/scripts]
+
+725. **DONE — roadmap-next-id helper now fails closed on helper-era duplicate ids before printing a next id** — follow-up to #724 after dogfood on origin/main 25ee5f3d showed `scripts/roadmap-next-id.sh` could print `1000` and exit 0 when a temp ROADMAP copy already contained two `999.` helper-era entries. This PR makes `roadmap-next-id.sh` resolve `roadmap-check-ids.sh` by its own script directory, run the checker with default helper-era min-id semantics before computing `highest+1`, keep stdout reserved for the single next id on success, and fail closed with a useful error if the checker is unavailable. Added focused pytest coverage for clean next-id output, duplicate fail-fast behavior, and missing-checker fail-closed behavior. **Verification:** `scripts/roadmap-next-id.sh ROADMAP.md` prints `725`; `scripts/roadmap-check-ids.sh ROADMAP.md` passes; a temp ROADMAP with duplicate `999.` exits nonzero and lists duplicate id 999 without printing a next id; `bash -n scripts/roadmap-next-id.sh scripts/roadmap-check-ids.sh` passes; `python -m pytest tests/test_roadmap_helpers.py -q` passes. Source: Jobdori dogfood follow-up on origin/main 25ee5f3d. [SCOPE: docs/scripts]