fix(gemini): strip native self prefixes before generateContent (#36141)

Strip `google/` and `gemini/` self-prefixes before native Gemini generateContent calls, and keep provider-normalization expectations aligned.

hermes_cli/model_normalize.py

@@ -84,7 +84,6 @@ _STRIP_VENDOR_ONLY_PROVIDERS: frozenset[str] = frozenset({
 
 # Providers whose native naming is authoritative -- pass through unchanged.
 _AUTHORITATIVE_NATIVE_PROVIDERS: frozenset[str] = frozenset({
-    "gemini",
     "huggingface",
 })
 
@@ -103,6 +102,8 @@ _MATCHING_PREFIX_STRIP_PROVIDERS: frozenset[str] = frozenset({
     "arcee",
     "ollama-cloud",
     "custom",
+    "gemini",
+    "xai",
 })
 
 # Providers whose APIs require lowercase model IDs.  Xiaomi's