- plugins/image_gen/xai: merge the live /v1/image-generation-models catalog
(5-min cache, 10s timeout, static-table fallback when offline/unauth)
into the picker so new xAI Imagine models appear automatically the day
they launch, with generic metadata until curated text is added.
- Add grok-imagine-image-2.0 to the curated static table (typography/
layout-aware model, API-available since Aug 8 2026).
- Edits honor an explicitly selected image-input-capable model
(e.g. grok-imagine-image-2.0) instead of always forcing
grok-imagine-image-quality; quality remains the default edit baseline.
- Tests: hermetic autouse fixture keeps unit runs offline; new coverage
for live-merge, unknown-future-model selection, offline fallback, and
edit-model resolution. Docs model table updated (en + zh-Hans).
Live-verified: /image-generation-models returns grok-imagine-image,
grok-imagine-image-2.0, grok-imagine-image-quality; real generation with
2.0 succeeded end to end.
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