fix(frontend): align Vertex Gemini endpoint controls

frontend/src/features/providers/components/endpoint-default-paths.ts

@@ -0,0 +1,47 @@
+interface ApiFormatPathDefinition {
+  value: string
+  default_path: string
+}
+
+export function normalizeEndpointApiFormat(apiFormat: string): string {
+  switch (apiFormat.trim().toLowerCase()) {
+    default:
+      return apiFormat.trim().toLowerCase()
+  }
+}
+
+function isCodexUrl(baseUrl: string): boolean {
+  const url = baseUrl.replace(/\/+$/, '')
+  return url.includes('/backend-api/codex') || url.endsWith('/codex')
+}
+
+export function getDefaultEndpointPath(params: {
+  apiFormat: string
+  providerType?: string | null
+  baseUrl?: string
+  apiFormats: ApiFormatPathDefinition[]
+}): string {
+  const providerType = (params.providerType || '').toLowerCase()
+  const normalizedApiFormat = normalizeEndpointApiFormat(params.apiFormat)
+  if (providerType === 'vertex_ai') {
+    if (normalizedApiFormat === 'gemini:generate_content') {
+      return '/v1/projects/{project_id}/locations/{region}/publishers/google/models/{model}:{action}'
+    }
+    if (normalizedApiFormat === 'gemini:embedding') {
+      return '/v1/projects/{project_id}/locations/{region}/publishers/google/models/{model}:predict'
+    }
+    if (normalizedApiFormat === 'claude:messages') {
+      return '/v1/projects/{project_id}/locations/{region}/publishers/anthropic/models/{model}:{action}'
+    }
+  }
+
+  const format = params.apiFormats.find(f => f.value === normalizedApiFormat)
+  const defaultPath = format?.default_path || ''
+  const isCodex = providerType
+    ? providerType === 'codex'
+    : (!!params.baseUrl && isCodexUrl(params.baseUrl))
+  if (normalizedApiFormat === 'openai:responses' && isCodex) {
+    return '/responses'
+  }
+  return defaultPath
+}