Switch Grok and OpenCode Go Responses to the shared packages

[TheGreatAxios]

Summary

Host Grok and OpenCode Go Responses adapters bake @corbits/xai-provider and @corbits/openai-responses factories while keeping provider ids and option keys. Grok streams terminate on response.completed via the package isStreamTerminal. In-tree Grok and OpenCode Go Responses adapter forks are gone.

The host adapters were forks of the Codex Responses client. The packages now own that protocol, including Grok's x-grok-* headers and the missing stream-terminal check. The host Grok adapter never ended on response.completed, so streams could hang waiting for [DONE].

• Provider ids stay grok-responses and openai-responses. The package's openai-compatible-responses id is not registered, so stored reasoning signatures stay valid.
• Host option keys stay; the factory maps them to package sessionIdOption / fromOption.
• Exactly one @intx/inference copy must resolve (packages declare it as a peer).
• Host retains billing URL, discovery URL, usage snapshots, and the src/auth/xai TUI (those move under CL-7424, not here).

Verification

• bun run typecheck, bun run build, and bun run test pass
• bun run check passes
• Adapter tests assert the same wire body against the package, plus isStreamTerminal present

Fixes CL-7423

[linear-code]

CL-7423