C5: review-loop worker default route clodex → claude + plumbing removal

[SSFSKIM]

Problem & intent

Flip the review-loop workers' default model route from the clodex gateway to plain Claude, and delete the nested-codex plumbing only the codex engine needed. Touches skills/reviewing-prs/scripts/review-dispatch.sh + land-dispatch.sh (default route) and the engine path's TLS/CODEX_HOME/seatbelt workarounds. Child C5 of docs/doperpowers/specs/2026-07-26-claude-review-stack-roadmap.md.

Constraints

• X4: after the flip, engine:codex label = clodex gateway opt-in (worker MODEL route only — post-C5 the loop's review engine is argus on EVERY route); engine:claude becomes redundant-but-valid.
• The "codex as fallback" in the roadmap's parent acceptance lives in interactive/execplan contexts only — the nested-codex plumbing has no remaining loop caller and is deleted.

Success criteria

• A label-less review dispatch spawns a plain-Claude worker end to end.
• engine:codex still opts back into the gateway route.
• The removed plumbing has no remaining caller.

Open questions

• (none expected beyond the child's own verification design)

Decision log

• Sequenced after C4 so the plumbing removal lands with the flip (roadmap Decision Log).

[SSFSKIM]

[board] ready-for-agent: roadmap C5 — blocked-by C4