渠道: Base URL 智能识别前缀/完整端点 + API 格式垂直堆叠

- upstreamURL 按内容智能拼接: 完整端点直接用 / 含 /v1 只拼资源路径 / 纯域名拼全路径
- resolveBaseURL 不再去 /v1, 交网关识别
- 渠道表 API 格式改垂直堆叠, 显示短标识 chat/completions / responses / messages
- 前端 Base URL 提示支持前缀或完整端点

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/views/admin/ChannelsView.vue

@@ -2,12 +2,12 @@
 import { onMounted, reactive, ref } from 'vue'
 import { http, errMsg } from '@/api/client'
 import { useToastStore } from '@/stores/toast'
-import { PROTOCOL_OPTIONS, protocolName } from '@/lib/protocol'
+import { PROTOCOL_OPTIONS, protocolShort } from '@/lib/protocol'
 import Button from '@/components/ui/Button.vue'
 import Input from '@/components/ui/Input.vue'
 import Modal from '@/components/ui/Modal.vue'
 import Badge from '@/components/ui/Badge.vue'
-import type { Channel } from '@/types'
+import type { Channel, ChannelModelMapping } from '@/types'
 
 const toast = useToastStore()
 const channels = ref<Channel[]>([])
@@ -154,12 +154,12 @@ onMounted(load)
             <tr v-for="ch in channels" :key="ch.id" class="table-row">
               <td class="px-4 py-2.5 text-ink">{{ ch.name }}</td>
               <td class="px-4 py-2.5">
-                <div class="flex flex-wrap gap-1">
-                  <span
+                <div class="flex flex-col gap-0.5">
+                  <code
                     v-for="f in ch.formats || []"
                     :key="f"
-                    class="rounded-full bg-surface2 px-2 py-0.5 text-[10px] leading-4 text-muted"
-                  >{{ protocolName(f) }}</span>
+                    class="font-mono text-[11px] leading-4 text-muted"
+                  >{{ protocolShort(f) }}</code>
                 </div>
               </td>
               <td class="px-4 py-2.5 font-mono text-xs text-muted">{{ ch.base_url }}</td>
@@ -215,8 +215,8 @@ onMounted(load)
         <Input
           v-model="form.base_url"
           label="Base URL（可选）"
-          placeholder="https://api.openai.com"
-          hint="留空按供应商默认；可填完整地址，如 https://api.openai.com/v1"
+          placeholder="https://api.openai.com/v1"
+          hint="支持前缀或完整端点，如 https://api.openai.com/v1 或 https://api.openai.com/v1/chat/completions；留空按供应商默认"
         />
         <Input
           v-model="form.api_key"