Grok Build /model switch fails: cannot serialize RuntimeKey::Other

Summary

After logging into Grok Build via the managed ACP provider, selecting a Grok Build model in /model fails before the switch reaches the server:

Failed to request model switch: cannot serialize tagged newtype variant RuntimeKey::Other containing a string

Reproduction

1. Authenticate Grok Build (jcode login --provider grok-build).
2. Open /model.
3. Select a Grok Build route such as grok-build:grok-4.6 (api_method grok-build-acp).

Expected

The picker sends a structured SetRoute request and the session switches to Grok Build.

Actual

The client cannot serialize RuntimeKey::Other("grok-build-acp"). RuntimeKey is internally tagged (#[serde(tag = "kind")]), and serde cannot serialize a newtype variant that contains a string.

Grok Build routes use api_method = "grok-build-acp", which currently falls through to RuntimeKey::Other.

Environment

• Jcode with Grok Build ACP (grok-build-acp)
• Model picker route: grok-build:grok-4.6 via Grok Build (grok-build-acp)