Switchboard slice: embedded Vibe route registered disabled-by-default beside vibe-direct; parity acceptance + cutover criteria #1714

Part of the Vibe-embedding epic (ACP-hosted vibe-acp). Depends on the runtime, permission-bridge, auth, and usage children.

Scope — production-shaped slice, switchboard rules

• Register the embedded Vibe route in the deployed config (developing-today/code .opencode/opencode.jsonc) alongside vibe-direct, following the provider switchboard rule: definitions are never deleted; enablement is a flag (disabled_providers). The embedded route ships disabled by default.
• vibe-direct stays the live route until cutover criteria are met. Nothing about tonight's working route changes in this slice.

Parity acceptance (before any enablement)

• A fixed battery of representative prompts (plain chat, file-read reasoning, bash tool use, multi-turn continuation, a denied-permission case) runs through both routes; transcripts + usage compared. Embedded route must show: same model identity (mistral-vibe-cli-latest family), tool calls actually executed by the real agent, usage attributed (see usage child), no capability the shim has that the embedded route lacks (and the reverse noted — embedded gains the agent's own tools/skills/subagents by construction).
• Failure behavior: vibe-acp process death mid-turn surfaces as a session error, not a hang (the standing lesson from provider stalls).

Cutover criteria (Drew's word required)

1. Parity battery green.
2. Usage reconciliation green for a mixed-traffic day (usage child acceptance).
3. Auth acceptance green (keyring-only path, rotation proven).
4. Then: enable embedded as the first leg of the mistral route, shim demoted to fallback — one flag flip, reversible.
5. Shim retirement is a separate later decision after a clean burn period; its definition stays in the tree per switchboard rules until Drew orders removal.