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/openai.py

@@ -0,0 +1,65 @@
+"""OpenAI Models API capability reader.
+
+OpenAI's `/v1/models` list/retrieve shape currently provides model identity
+metadata only: `id`, `object`, `created`, and `owned_by`. Those fields prove
+availability, not model capabilities, so this reader keeps capabilities
+unknown unless OpenAI adds explicit capability fields to the API shape later.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from typing import Any
+
+from src import model_capabilities as mc
+from src.model_capability_readers.base import (
+    ModelCapabilityRecord,
+    VENDOR_OPENAI,
+    compact_str,
+    model_id_from,
+    openai_model_items,
+    stable_model_id_for,
+)
+
+
+vendor = VENDOR_OPENAI
+
+
+OFFICIAL_MODEL_FIELDS = frozenset({"id", "object", "created", "owned_by"})
+
+
+def record_from_model(
+    raw: Mapping[str, Any],
+    *,
+    endpoint_id: Any = "",
+    base_url: Any = "",
+) -> ModelCapabilityRecord | None:
+    model_id = model_id_from(raw, "id")
+    if not model_id:
+        return None
+
+    return ModelCapabilityRecord(
+        vendor=VENDOR_OPENAI,
+        model_id=model_id,
+        stable_model_id=stable_model_id_for(VENDOR_OPENAI, model_id, endpoint_id=endpoint_id, base_url=base_url),
+        display_name=compact_str(raw.get("name") or raw.get("display_name")),
+        capability=mc.unknown_capability(
+            source=mc.SOURCE_PROVIDER_READER,
+            confidence=mc.CONFIDENCE_UNKNOWN,
+        ),
+        raw=raw,
+    )
+
+
+def records_from_payload(
+    payload: Mapping[str, Any],
+    *,
+    endpoint_id: Any = "",
+    base_url: Any = "",
+) -> tuple[ModelCapabilityRecord, ...]:
+    records: list[ModelCapabilityRecord] = []
+    for item in openai_model_items(payload):
+        record = record_from_model(item, endpoint_id=endpoint_id, base_url=base_url)
+        if record:
+            records.append(record)
+    return tuple(records)