fix(channels): 追加模型时不再改写已留空的价格条目

渠道定价条目价格留空时按各模型官方默认价回退计费，但向这类条目追加
模型时，前端会用「第一个新增模型」的默认价回填整条价格字段，保存后
条目内所有模型被静默统一成同一个价格，造成少计费或多计费。

自动填充现在只作用于「空条目首次加入单个模型」：条目已有模型时追加、
或一次加入多个模型时都不再改写价格，留空条目继续按各模型默认价回退。

- 新增 PricingEntryCard.modelDefaultPrice.spec.ts 覆盖 4 种场景
- 把该 spec 加入 Makefile 的 FRONTEND_CRITICAL_VITEST，使 CI 覆盖该回归

Closes #7796

Makefile

@@ -21,7 +21,8 @@ FRONTEND_CRITICAL_VITEST := \
 	src/views/admin/__tests__/SettingsView.spec.ts \
 	src/features/channel-monitor-v2/__tests__/designSystem.structure.spec.ts \
 	src/features/channel-monitor-v2/__tests__/monitorFormat.spec.ts \
-	src/features/channel-monitor-v2/__tests__/monitorZoom.spec.ts
+	src/features/channel-monitor-v2/__tests__/monitorZoom.spec.ts \
+	src/components/admin/channel/__tests__/PricingEntryCard.modelDefaultPrice.spec.ts
 
 # 一键编译前后端
 build: build-backend build-frontend

frontend/src/components/admin/channel/PricingEntryCard.vue

@@ -411,9 +411,11 @@ async function onModelsUpdate(newModels: string[]) {
   const oldModels = props.entry.models
   emit('update', { ...props.entry, models: newModels })
 
-  // 只在新增模型且当前无价格时自动填充
+  // 仅在「空条目首次加入单个模型」时自动填充默认价：
+  // 条目已有模型时（即使价格留空、按各模型的官方默认价回退）追加模型不应改写整条价格，
+  // 一次加入多个模型也不应把第一个模型的价格套用到整条，否则条目内所有模型都会被静默改价。
   const addedModels = newModels.filter(m => !oldModels.includes(m))
-  if (addedModels.length === 0) return
+  if (oldModels.length !== 0 || addedModels.length !== 1) return
 
   // 检查是否所有价格字段都为空
   const e = props.entry

frontend/src/components/admin/channel/__tests__/PricingEntryCard.modelDefaultPrice.spec.ts

@@ -0,0 +1,108 @@
+import { flushPromises, shallowMount } from '@vue/test-utils'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import PricingEntryCard from '../PricingEntryCard.vue'
+import type { PricingFormEntry } from '../types'
+import channelsAPI from '@/api/admin/channels'
+
+vi.mock('@/api/admin/channels', () => ({
+  default: { getModelDefaultPricing: vi.fn() },
+}))
+
+vi.mock('vue-i18n', async importOriginal => ({
+  ...await importOriginal<typeof import('vue-i18n')>(),
+  useI18n: () => ({ t: (key: string) => key }),
+}))
+
+const getModelDefaultPricing = vi.mocked(channelsAPI.getModelDefaultPricing)
+
+function createEntry(models: string[] = []): PricingFormEntry {
+  return {
+    models,
+    billing_mode: 'token',
+    input_price: null,
+    output_price: null,
+    cache_write_price: null,
+    cache_read_price: null,
+    fast_multiplier: null,
+    flex_multiplier: null,
+    reasoning_effort_multipliers: null,
+    image_input_price: null,
+    image_output_price: null,
+    per_request_price: null,
+    intervals: [],
+    time_pricing: {
+      timezone: 'Asia/Shanghai',
+      weekdays_only: false,
+      periods: [],
+    },
+  }
+}
+
+function addModels(entry: PricingFormEntry, models: string[]) {
+  const wrapper = shallowMount(PricingEntryCard, { props: { entry } })
+  wrapper.findComponent({ name: 'ModelTagInput' }).vm.$emit('update:models', models)
+  return wrapper
+}
+
+const emittedEntries = (wrapper: ReturnType<typeof shallowMount>) =>
+  (wrapper.emitted('update') ?? []).map(e => e[0] as PricingFormEntry)
+
+describe('PricingEntryCard default price auto-fill', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    getModelDefaultPricing.mockResolvedValue({ found: true, input_price: 3e-6, output_price: 15e-6 })
+  })
+
+  it('auto-fills the default price when a model is added to an empty entry', async () => {
+    const wrapper = addModels(createEntry(), ['claude-opus-4-8'])
+    await flushPromises()
+
+    expect(getModelDefaultPricing).toHaveBeenCalledTimes(1)
+    expect(getModelDefaultPricing).toHaveBeenCalledWith('claude-opus-4-8')
+    expect(emittedEntries(wrapper).at(-1)).toMatchObject({
+      models: ['claude-opus-4-8'],
+      input_price: 3,
+      output_price: 15,
+    })
+  })
+
+  it('does not overwrite prices when appending a model to an entry that already has one', async () => {
+    const entry = createEntry(['claude-opus-4-7'])
+    const wrapper = addModels(entry, ['claude-opus-4-7', 'claude-opus-4-8'])
+    await flushPromises()
+
+    expect(getModelDefaultPricing).not.toHaveBeenCalled()
+    expect(emittedEntries(wrapper).at(-1)).toMatchObject({
+      models: ['claude-opus-4-7', 'claude-opus-4-8'],
+    })
+    for (const emitted of emittedEntries(wrapper)) {
+      expect(emitted.input_price).toBeNull()
+      expect(emitted.output_price).toBeNull()
+      expect(emitted.cache_write_price).toBeNull()
+      expect(emitted.cache_read_price).toBeNull()
+    }
+  })
+
+  it('does not auto-fill a shared price when several models are added to an empty entry at once', async () => {
+    const wrapper = addModels(createEntry(), ['claude-opus-4-7', 'claude-opus-4-8'])
+    await flushPromises()
+
+    expect(getModelDefaultPricing).not.toHaveBeenCalled()
+    expect(emittedEntries(wrapper).at(-1)).toMatchObject({
+      models: ['claude-opus-4-7', 'claude-opus-4-8'],
+      input_price: null,
+      output_price: null,
+    })
+  })
+
+  it('keeps manual prices untouched when a model is appended', async () => {
+    const entry = { ...createEntry(['claude-opus-4-7']), input_price: '1.5' }
+    const wrapper = addModels(entry, ['claude-opus-4-7', 'claude-opus-4-8'])
+    await flushPromises()
+
+    expect(getModelDefaultPricing).not.toHaveBeenCalled()
+    for (const emitted of emittedEntries(wrapper)) {
+      expect(emitted.input_price).toBe('1.5')
+    }
+  })
+})