feat(gateway): harden provider request execution

Preserve exact request payloads and model client surface and API operation explicitly.

Add Anthropic compatibility profiles, bounded stream commitment, and scoped OAuth retry behavior across provider transports.

apps/aether-gateway/src/ai_serving/planner/antigravity.rs

@@ -67,6 +67,7 @@ pub(crate) async fn build_antigravity_v1internal_provider_request(
         input.upstream_is_stream,
         input.parts.uri.query(),
         None,
+        None,
         Some(&payload.body),
     )
     .ok_or(AntigravityV1InternalRequestError::UpstreamUrlUnavailable)?;