test(forge): add CI guard against duplicate provider model entries

Adds a lightweight smoke test that fails when any provider's
model list in _PROVIDER_MODELS contains duplicate entries.

- Runs in <1s
- Explicit regression guard for PR #225 kimi-coding duplicates
- Closes #232

tests/test_provider_models_no_duplicates.py

@@ -0,0 +1,23 @@
+"""Lightweight smoke test to ensure provider model catalogs contain no duplicate entries."""
+
+from hermes_cli.models import _PROVIDER_MODELS
+
+
+def test_provider_models_have_no_duplicates() -> None:
+    """Every provider's model list must contain unique model IDs."""
+    failures = []
+    for provider_id, models in _PROVIDER_MODELS.items():
+        seen = set()
+        dups = [m for m in models if m in seen or seen.add(m)]
+        if dups:
+            failures.append(f"  {provider_id}: duplicates {dups}")
+    if failures:
+        raise AssertionError(
+            "Duplicate model IDs found in _PROVIDER_MODELS:\n" + "\n".join(failures)
+        )
+
+
+def test_kimi_coding_no_duplicates() -> None:
+    """Explicit regression guard for PR #225."""
+    models = _PROVIDER_MODELS.get("kimi-coding", [])
+    assert len(models) == len(set(models)), f"Duplicates in kimi-coding: {models}"