Use configurable Model Target failures in CLI tests

[adamtheturtle]

Summary

After VWS-Python/vws-python-mock#3495 is complete and released, update vws-python-mock and exercise the remaining Model Target error messages through public CLI commands.

Current state

#2513 replaced method patching with public MockVWS behavior wherever the mock can represent the response. The following defensive branches remain excluded from coverage because the released mock cannot currently produce them:

• ModelTargetAuthenticationError after OAuth succeeds;
• generic ModelTargetError, with and without a message;
• the Model Target ServerError fallback.

The source comments link to the upstream feature request.

Acceptance criteria

• Update vws-python-mock to the release containing Support configurable Model Target failure responses vws-python-mock#3495.
• Add public CLI tests for authentication-style, generic JSON, generic non-JSON, and 5xx Model Target responses.
• Exercise the real command, ModelTargetService, transport, exception mapping, and CLI output path.
• Remove the corresponding # pragma: no cover annotations and temporary upstream comments.
• Do not patch client methods or test private formatter functions.
• Preserve 100% branch coverage and pass all project quality gates.

Blocked by

• Support configurable Model Target failure responses vws-python-mock#3495