Add hermes_cli.xai_retirement module that walks a Hermes config and
flags references to models being retired by xAI on May 15, 2026 per
the official migration guide.
Pure logic + dataclass, no I/O — testable in isolation and reusable
from a future hermes migrate xai sub-command.
Mappings (per https://docs.x.ai/developers/migration/may-15-retirement):
- grok-4 / grok-4-0709 -> grok-4.3
- grok-4-fast{,-reasoning,-non-reasoning} -> grok-4.3 (+reasoning_effort=none for non-reasoning)
- grok-4-1-fast{,-reasoning,-non-reasoning} -> grok-4.3 (+reasoning_effort=none for non-reasoning)
- grok-code-fast-1 -> grok-4.3
- grok-imagine-image-pro -> grok-imagine-image-quality
Slots scanned: principal.model, auxiliary.<any>.model (introspective),
delegation.model, tts.xai.model, plugins.image_gen.xai.model. Provider
prefix x-ai/ is normalized.
33 unit tests covering edge cases (empty/non-dict config, valid models,
ambiguous variants, all retired slots, formatter).
