feat(model-test): wire image previews into provider tests

frontend/src/features/providers/components/provider-tabs/ModelsTab.vue

@@ -272,6 +272,7 @@ import {
   normalizeModelTestMappedModelSelection,
   parseModelTestRequestHeadersDraft,
   parseModelTestRequestBodyDraft,
+  selectPreferredModelTestEndpoint,
   syncModelTestRequestBodyDraft,
 } from './model-test-request'
 
@@ -586,7 +587,7 @@ async function testModelConnection(model: Model) {
   }
 
   pendingTestModel.value = model
-  selectedTestEndpoint.value = activeEndpoints.value[0] ?? null
+  selectedTestEndpoint.value = selectPreferredModelTestEndpoint(model, activeEndpoints.value)
   const requestedModelName = getModelTestRequestedModelName(model)
   selectedTestMappedModelName.value = null
   testRequestHeadersResetValue.value = buildDefaultModelTestRequestHeaders()
@@ -594,6 +595,7 @@ async function testModelConnection(model: Model) {
   testRequestBodyResetValue.value = buildDefaultModelTestRequestBody(
     requestedModelName,
     selectedTestEndpoint.value?.api_format,
+    model,
   )
   testRequestBodyDraft.value = testRequestBodyResetValue.value
   modelTest.testResult.value = null
@@ -619,7 +621,11 @@ function syncTestRequestBodyModel() {
   if (!modelName) return
 
   const resetDraft = testRequestBodyResetValue.value
-    || buildDefaultModelTestRequestBody(modelName, selectedTestEndpoint.value?.api_format)
+    || buildDefaultModelTestRequestBody(
+      modelName,
+      selectedTestEndpoint.value?.api_format,
+      pendingTestModel.value,
+    )
   const next = syncModelTestRequestBodyDraft(
     testRequestBodyDraft.value,
     testRequestBodyResetValue.value,
@@ -637,6 +643,7 @@ function resetTestRequestBodyForSelectedEndpoint() {
   const nextResetValue = buildDefaultModelTestRequestBody(
     modelName,
     selectedTestEndpoint.value?.api_format,
+    pendingTestModel.value,
   )
   const next = syncModelTestRequestBodyDraft(
     testRequestBodyDraft.value,