fix(provider): 将rust分支的gemini cli端点行为对齐到python分支 (#321)

* fix(provider): 对齐 Vertex/Gemini 上游发包与 Python master

- provider-transport: 为 custom+aiplatform 推断 Vertex API key 上下文并统一 URL 构建顺序，复用共享 request_url 构建最终上游地址
- ai-pipeline/gateway: Vertex Gemini 路径改为仅使用 URL query key，不再向上游附带 x-goog-api-key header；同步对齐 standard/admin/test-connection/runtime miss 摘要中的最终 URL
- gemini conversion: 按 Python master 输出 Gemini 请求体，补齐 system_instruction / generation_config / tool_config / function_declarations 形态，并移植 Gemini schema 清洗逻辑
- scheduler/executor: 将最终 upstream_url、mapped_model、key_name 写入候选 extra_data，运行时 miss 诊断优先展示真实展开后的上游 URL 便于服务器排障

* fix(provider): 修复 Vertex provider 测试与本地调度链路

* fix(provider): 对齐 Vertex 本地执行与 Rust CI

apps/aether-gateway/src/executor/outcome.rs

@@ -619,8 +619,9 @@ async fn load_runtime_miss_candidate_contexts(
                     &candidate,
                     "selected_provider_model_name",
                 ),
-                endpoint_url: endpoint
-                    .and_then(|value| build_runtime_miss_candidate_endpoint_url(value, decision)),
+                endpoint_url: endpoint.and_then(|value| {
+                    build_runtime_miss_candidate_endpoint_url(&candidate, value, decision)
+                }),
                 candidate,
             }
         })
@@ -671,9 +672,14 @@ fn candidate_extra_data_string(candidate: &StoredRequestCandidate, key: &str) ->
 }
 
 fn build_runtime_miss_candidate_endpoint_url(
+    candidate: &StoredRequestCandidate,
     endpoint: &StoredProviderCatalogEndpoint,
     decision: Option<&GatewayControlDecision>,
 ) -> Option<String> {
+    if let Some(upstream_url) = candidate_extra_data_string(candidate, "upstream_url") {
+        return Some(upstream_url);
+    }
+
     let path = endpoint
         .custom_path
         .as_deref()