0.1.5-rc5

Hand a dsh model whose provider declares no wire protocol over instead of refusing it, so a hosted engine reaches dsh's endpoint rather than quietly using its own.

• Admission for the model handover now needs only a non-empty baseURL and a resolvable credential; api is a hint, not a gate. A declared protocol always wins, a shipped route is filled in by a one-entry table (deepseek-official -> openai-completions), and anything still unknown hands over api: undefined for each engine to degrade on its own.
• codex: the provider override now carries name (without it app-server died at config load), and openai-completions no longer maps to the chat wire upstream removed -- writing it is now a fatal config error. Both failures reached the driver only as "codex app-server process exited unexpectedly".
• pi alone cannot express a protocol-less provider, so its driver drops such a handover rather than writing a models.json pi rejects.
• Verified against a live endpoint: the request lands on <baseURL>/responses and the gateway answers. See docs/optimization-backlog.md BL-01 and BL-19 for what remains unproven.

Harness peers stay at 0.1.5-rc.2.