Delete the stale literal `_PROVIDER_MODELS["ai-gateway"]` (gpt-5,
gemini-2.5-pro, claude-4.5 — outdated the moment PR #13223 landed with
its curated `AI_GATEWAY_MODELS` snapshot) and derive it from
`AI_GATEWAY_MODELS` instead, so the picker tuples and the bare-id
fallback catalog stay in sync automatically. Also fixes
`get_default_model_for_provider('ai-gateway')` to return kimi-k2.6
(the curated recommendation) instead of claude-opus-4.6.
When the live Vercel AI Gateway catalog exposes a Moonshot model with
zero input AND output pricing, it's promoted to position #1 as the
recommended default — even if the exact ID isn't in the curated
AI_GATEWAY_MODELS list. This enables dynamic discovery of new free
Moonshot variants without requiring a PR to update curation.
Paid Moonshot models are unaffected; falls back to the normal curated
recommended tag when no free Moonshot is live.
- Curated AI_GATEWAY_MODELS list in hermes_cli/models.py (OSS first,
kimi-k2.5 as recommended default).
- fetch_ai_gateway_models() filters the curated list against the live
/v1/models catalog; falls back to the snapshot on network failure.
- fetch_ai_gateway_pricing() translates Vercel's input/output field
names to the prompt/completion shape the shared picker expects;
carries input_cache_read / input_cache_write through unchanged.
- get_pricing_for_provider() now handles ai-gateway.
- _model_flow_ai_gateway() provides a guided URL prompt when no key
is set and a pricing-column picker; routes ai-gateway to it instead
of the generic api-key flow.
