Prevent helper-era ROADMAP id collisions before review (#3115)

Add a lightweight ROADMAP duplicate-id guard and wire it into the low-risk docs/pre-push paths so optimistic append collisions introduced after the next-id helper are caught before merge.

Constraint: Current ROADMAP contains legacy numbered lists and pre-helper duplicate low ids, so the default guard checks helper-era ids >=723 while preserving --min-id 1 for a future strict audit.
Rejected: Fail CI on every numeric duplicate in the whole historical ROADMAP | current main would fail before this PR because old prose/list numbering is already duplicated.
Confidence: high
Scope-risk: narrow
Directive: Keep roadmap-next-id.sh paired with roadmap-check-ids.sh when changing ROADMAP append workflows.
Tested: bash -n scripts/roadmap-check-ids.sh scripts/roadmap-next-id.sh .github/hooks/pre-push; scripts/roadmap-check-ids.sh; temp ROADMAP copy with duplicate 723 failed nonzero and listed id 723; SKIP_CLAW_PRE_PUSH_BUILD=1 .github/hooks/pre-push; git diff --check; python3 .github/scripts/check_doc_source_of_truth.py; python3 .github/scripts/check_release_readiness.py
Not-tested: full cargo workspace build/test because this is docs/scripts-only and the local pre-push cargo build was smoke-tested with its documented skip path.

ROADMAP.md

@@ -7613,3 +7613,5 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 722. **ROADMAP #721 re-entry after rebase conflict: `claw config mcp|sandbox|permissions|skills|agents` returned `unsupported_config_section` — code fix is in `6e44da10`** (main.rs changes preserved through rebase, only ROADMAP.md was conflict-resolved to Gaebal's version). Both text and JSON config section handlers now support `mcp`, `sandbox`, `permissions`, `skills`, `agents`; error envelope includes `supported_sections:[]`. Source: Jobdori dogfood on `02d1f6a0`, 2026-05-26.
 
 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]