fix(models): keep curated-first ordering in live+curated merge; use pure-catalog helper in validation

The generic live+curated merge (commit 630b438) seeded the merged list
from live results, demoting curated-only models below live ones. That
regressed #46309, which deliberately surfaces the newest curated model
(kimi-k2.7-code) FIRST in the native picker even when the live /models
listing lags. Restore curated-first ordering: curated entries lead (in
catalog order), live-only entries are appended for discovery. This keeps
the #46850 fix (zai glm-5.2 now appears) without the kimi regression.

Also switch the validate_requested_model curated fallback (commit
ee7b8a4) from provider_model_ids() — which triggers a second, uncached
live /models fetch with its own 8s timeout and may resolve different
credentials than the api_key/base_url just probed — to the pure-catalog
helper _model_in_provider_catalog(). Membership is checked against the
shipped catalog only, with no extra network call.

Tests: restore the curated-first assertion in
test_kimi_coding_live_catalog_does_not_hide_curated_k2_7_code; update
the new merge tests to curated-first semantics; de-circularize the
validation fallback tests to patch _PROVIDER_MODELS (the real source)
instead of mocking the function under test.

tests/hermes_cli/test_models_dev_preferred_merge.py

@@ -114,8 +114,8 @@ class TestProviderModelIdsPreferred:
             patch("providers.base.ProviderProfile.fetch_models", return_value=["kimi-k2.6"]),
         ):
             out = provider_model_ids("kimi-coding")
-        # Live-first order; curated-only (k2.7-code) appended after live
-        assert out[:2] == ["kimi-k2.6", "kimi-k2.7-code"]
+        # Curated-first order; curated newest (k2.7-code) stays ahead of live.
+        assert out[:2] == ["kimi-k2.7-code", "kimi-k2.6"]
 
     def test_kimi_setup_flow_uses_same_coding_plan_catalog(self):
         """The setup wizard must not carry a stale duplicate Kimi model list."""