cli: TUI fails to connect to password-protected explicit server via --server

Summary

opencode --server <url> against a password-protected opencode serve always fails the startup health check with UnsupportedContentType, in all credential forms. The same URL works with opencode run and opencode api, so the server side is fine — only the TUI startup path fails.

Environment

• opencode version: 2.0.5
• OS: Linux 7.2.6-arch2-1 (linux x64)
• Terminal: Unavailable: terminal environment variables are not set
• Shell: /usr/bin/bash
• Install/channel: latest
• Active plugins: Omitted at reporter's request

Reproduction

1. Start a password-protected server: opencode serve --hostname 0.0.0.0 --port 4096 with OPENCODE_SERVER_PASSWORD set.
2. Run opencode --server http://127.0.0.1:4096 — fails.
3. Retry with credentials in URL (http://opencode:<pass>@127.0.0.1:4096) and as ?auth_token=<base64(user:pass)> — both fail identically.
4. Run opencode run --server "<auth_token form>" "hi" — succeeds. opencode api --server "<userinfo form>" get /api/status — succeeds.

Expected Behavior

The TUI connects to the explicit server the same way run and api do.

Actual Behavior

Error: Server at http://127.0.0.1:4096 did not provide a compatible V2 health response ... [cause]: ClientError: UnsupportedContentType

Unauthenticated /api/status returns 401 with an empty body, so the TUI check appears to send no credentials in any URL form.

Additional Context

• The cli.json schema has no default-server field, so --server cannot be defaulted; aliases/functions are the only workaround, and they hit this bug.
• No doc describes TUI --server authentication (CLI, Web, Commands, and client guides checked).