C6: implement worker default route clodex → claude

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Problem & intent

Flip the implement worker's default model route from the clodex gateway (GPT via cliproxy) to plain Claude in skills/implementing-tickets/scripts/implement-dispatch.sh. Opus 5-class models now beat the GPT route for implementation; the human has ruled a performance bench unnecessary. Child C6 of docs/doperpowers/specs/2026-07-26-claude-review-stack-roadmap.md — independent of the review-stack sequence, dispatchable now.

Constraints

• X4 (route label semantics): engine:codex label must still opt a ticket back into the clodex gateway route; engine:claude becomes redundant-but-valid and must not break.
• This is the default flip ONLY — do not remove the gateway route or its settings plumbing (retiring clodex entirely is deferred to a later unit; roadmap Deferred section).
• Mind the dispatcher's persistence contract: the codex route persists DAEMON_CLAUDE_SETTINGS/EFFORT into the daemon registry meta so resumes keep the gateway. The claude-default path must keep resumes consistent too.
• Check the sweep path (board-sweep.sh → implement-dispatch.sh --sweep) and any docs that state the default (issue-tracker SKILL.md dispatch ritual step 2 says "→ default codex"; operation-manual mentions the default route) — update prose that names the old default.

Success criteria

• A label-less implement dispatch spawns a plain-Claude worker (no gateway env, model inherits/pins per the claude route).
• A ticket labeled engine:codex still spawns a gateway-routed worker.
• Documentation that states the default route reflects claude.

Open questions

• Whether $WORKER_ENGINE env default should also flip or stay as an override knob — recommend: flip the final fallback, keep the env override working.

Decision log

• Split out of C5 with no edges: independent shippable, blocked by nothing (roadmap Decision Log). No bench (human ruling, Opus 5 rationale).

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[board] ready-for-agent: roadmap C6 — independent, dispatchable now

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[gate] pass — claude/DIRECT: one-line fallback flip in implement-dispatch.sh plus the prose that names the old default; every fork (env-override semantics, model pin, resume persistence) is answered by the ticket or by the existing spawn/resume contract.

[SSFSKIM]

[board] in-review: default route flipped to claude; gateway preserved behind engine:codex