feat(models): define capability schema and readers (#2739)

* feat(models): define capability schema and readers

* fix(models): harden Google catalog probing

Restrict native catalog probing to the Gemini host, keep provider keys out of request URLs, filter non-chat model resources, and preserve the manual refresh default in the built-in Google add flow.

src/model_capability_readers/google.py

@@ -0,0 +1,60 @@
+"""Google Gemini model metadata reader."""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from typing import Any
+
+from src.model_capability_readers import google_ai_studio_mapping as ai_studio
+from src.model_capability_readers.base import (
+    ModelCapabilityRecord,
+    VENDOR_GOOGLE,
+    as_list,
+    compact_str,
+    stable_model_id_for,
+)
+
+
+vendor = VENDOR_GOOGLE
+
+
+def _model_items(payload: Mapping[str, Any]) -> tuple[Mapping[str, Any], ...]:
+    models = payload.get("models") if isinstance(payload, Mapping) else None
+    if models is None and isinstance(payload, Mapping) and payload.get("name"):
+        models = [payload]
+    return tuple(item for item in as_list(models) if isinstance(item, Mapping))
+
+
+def record_from_model(
+    raw: Mapping[str, Any],
+    *,
+    endpoint_id: Any = "",
+    base_url: Any = "",
+) -> ModelCapabilityRecord | None:
+    model_id = ai_studio.google_model_id(raw)
+    if not model_id:
+        return None
+
+    return ModelCapabilityRecord(
+        vendor=VENDOR_GOOGLE,
+        model_id=model_id,
+        stable_model_id=stable_model_id_for(VENDOR_GOOGLE, model_id, endpoint_id=endpoint_id, base_url=base_url),
+        display_name=compact_str(raw.get("displayName")) or model_id,
+        capability=ai_studio.capability_from_model(raw),
+        deterministic_controls=ai_studio.deterministic_controls_from_model(raw),
+        raw=raw,
+    )
+
+
+def records_from_payload(
+    payload: Mapping[str, Any],
+    *,
+    endpoint_id: Any = "",
+    base_url: Any = "",
+) -> tuple[ModelCapabilityRecord, ...]:
+    records: list[ModelCapabilityRecord] = []
+    for item in _model_items(payload):
+        record = record_from_model(item, endpoint_id=endpoint_id, base_url=base_url)
+        if record:
+            records.append(record)
+    return tuple(records)