feat(review): show format rules summary per target journal

- New summary row: shows the journal's rules (even if no diff applies)
- Fixes user confusion when switching journals yields same diff
- When all rules are null: 'no explicit format requirements'
- Vitest: add case for summary rendering

tests/frontend/unit/edu/reformat.rules-summary.test.js

@@ -0,0 +1,123 @@
+// tests/frontend/unit/edu/reformat.rules-summary.test.js
+//  目标期刊规则摘要行（data-testid="rf-rules-summary"）：
+//  1) 有规则字段 + 有 diff → 摘要 + "已修改 N 处"
+//  2) 规则全 null + diff=0 → "无强制约束" + "样本已满足该刊要求，无需修改"
+//  背景：GB/BMC PB/Rice 规则相同、Frontiers 几乎无规则，用户切换期刊看不到 diff 差异，
+//  即使 diff=0 也要展示"该刊要求什么"，消除"没生效"错觉。
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { mount } from '@vue/test-utils';
+import { createPinia, setActivePinia } from 'pinia';
+import ReformatPanel from '../../../../ui/src/components/edu/panels/ReformatPanel.vue';
+
+vi.mock('../../../../ui/src/api/review.js', async (importOriginal) => {
+  const actual = await importOriginal();
+  return {
+    ...actual,
+    getJournals: vi.fn().mockResolvedValue({ ok: true, items: [] }),
+    getDirectory: vi.fn(),
+    reformatTex: vi.fn(),
+    compileTex: vi.fn(),
+  };
+});
+
+import { useEduStore } from '../../../../ui/src/stores/edu.js';
+
+function mountWithResult(eduSeed) {
+  const pinia = createPinia();
+  setActivePinia(pinia);
+  const edu = useEduStore();
+  Object.assign(edu, eduSeed);
+  const wrapper = mount(ReformatPanel, { global: { plugins: [pinia] } });
+  return { wrapper, edu };
+}
+
+function resultWith(rules, changes) {
+  return {
+    ok: true,
+    job_id: 'abc123def456',
+    modified_tex: 'x',
+    changes,
+    warnings: [],
+    meta: {
+      filename: 'paper.tex',
+      journal_name: 'Molecular Plant',
+      rules_source: 'official',
+      rules_note: 'journals.json 期刊专属规则',
+      rules,
+    },
+  };
+}
+
+describe('ReformatPanel 目标期刊规则摘要', () => {
+  beforeEach(() => {
+    global.fetch = vi.fn().mockRejectedValue(new Error('no network'));
+    if (!URL.createObjectURL) URL.createObjectURL = vi.fn(() => 'blob:mock');
+    if (!URL.revokeObjectURL) URL.revokeObjectURL = vi.fn();
+  });
+
+  it('1) 有规则字段 + 有 diff → 摘要列出字段且标注"已修改 N 处"', async () => {
+    // Molecular Plant 真实规则形态：12pt / 1.5 / author_year（font/margin null 不显示）
+    const { wrapper } = mountWithResult({
+      reformatStatus: 'ready',
+      reformatResult: resultWith(
+        {
+          min_font_pt: 12, min_margin_mm: null, min_line_spacing: 1.5,
+          refs_style: 'author_year', max_pages: null, min_figures: null, max_fonts: null,
+        },
+        [
+          { line: 1, original: 'a', modified: 'b', reason: 'r', rule_key: 'font_pt', action: 'modified' },
+          { line: 3, original: 'a', modified: 'b', reason: 'r', rule_key: 'line_spacing', action: 'modified' },
+          { line: 4, original: 'a', modified: 'b', reason: 'r', rule_key: 'bib_style', action: 'modified' },
+        ],
+      ),
+    });
+    await wrapper.vm.$nextTick();
+    const el = wrapper.find('[data-testid="rf-rules-summary"]');
+    expect(el.exists()).toBe(true);
+    const text = el.text();
+    expect(text).toContain('1.5 倍行距');
+    expect(text).toContain('作者-年份引用');
+    expect(text).toContain('字号 ≥12pt');
+    expect(text).not.toContain('null');
+    expect(text).not.toContain('边距'); // min_margin_mm=null → 不显示
+    expect(text).toContain('已修改 3 处');
+  });
+
+  it('2) 规则全 null + diff=0 → "无强制约束" + "样本已满足该刊要求，无需修改"', async () => {
+    const { wrapper } = mountWithResult({
+      reformatStatus: 'ready',
+      reformatResult: resultWith(
+        {
+          min_font_pt: null, min_margin_mm: null, min_line_spacing: null,
+          refs_style: null, max_pages: null, min_figures: null, max_fonts: null,
+        },
+        [],
+      ),
+    });
+    await wrapper.vm.$nextTick();
+    const el = wrapper.find('[data-testid="rf-rules-summary"]');
+    expect(el.exists()).toBe(true);
+    const text = el.text();
+    expect(text).toContain('该刊官网未规定明确格式要求，无强制约束');
+    expect(text).toContain('样本已满足该刊要求，无需修改');
+    expect(text).not.toContain('已修改');
+  });
+
+  it('3) 双倍行距 + Vancouver（GB/BMC/Rice 形态）→ 正确映射中文标签', async () => {
+    const { wrapper } = mountWithResult({
+      reformatStatus: 'ready',
+      reformatResult: resultWith(
+        {
+          min_font_pt: null, min_margin_mm: null, min_line_spacing: 2.0,
+          refs_style: 'vancouver', max_pages: null, min_figures: null, max_fonts: null,
+        },
+        [{ line: 3, original: 'a', modified: 'b', reason: 'r', rule_key: 'line_spacing', action: 'modified' }],
+      ),
+    });
+    await wrapper.vm.$nextTick();
+    const text = wrapper.find('[data-testid="rf-rules-summary"]').text();
+    expect(text).toContain('双倍行距');
+    expect(text).toContain('Vancouver 引用');
+    expect(text).toContain('已修改 1 处');
+  });
+});

ui/src/components/edu/panels/ReformatPanel.vue

@@ -118,6 +118,31 @@ const structWarnings = computed(() => result.value?.warnings || []);
 const modifiedCount = computed(() => changes.value.filter((c) => c.action === 'modified').length);
 const suggestCount = computed(() => changes.value.filter((c) => c.action === 'warning').length);
 const sourceLabel = computed(() => SOURCE_LABEL[meta.value?.rules_source] || meta.value?.rules_source || '—');
+// 目标期刊规则摘要：只显示有值字段（null 不显示）；全 null → 明确说明无强制约束。
+// 目的：diff=0 时（如 Frontiers / GB↔BMC 互切）也能看到"该刊要求什么"，消除"没生效"错觉。
+const _REFS_LABEL = { vancouver: 'Vancouver 引用', apa: 'APA 引用', author_year: '作者-年份引用' };
+const rulesSummary = computed(() => {
+  const r = meta.value?.rules;
+  if (!r || typeof r !== 'object') return null;
+  const parts = [];
+  const ls = r.min_line_spacing;
+  if (typeof ls === 'number' && ls > 0) {
+    if (ls <= 1.05) parts.push('单倍行距');
+    else if (Math.abs(ls - 1.5) < 0.01) parts.push('1.5 倍行距');
+    else if (ls >= 1.95) parts.push('双倍行距');
+    else parts.push(`行距 ≥${ls} 倍`);
+  }
+  if (r.refs_style && _REFS_LABEL[r.refs_style]) parts.push(_REFS_LABEL[r.refs_style]);
+  if (typeof r.min_font_pt === 'number') parts.push(`字号 ≥${r.min_font_pt}pt`);
+  if (typeof r.min_margin_mm === 'number') parts.push(`边距 ≥${r.min_margin_mm}mm`);
+  if (!parts.length) return '该刊官网未规定明确格式要求，无强制约束';
+  return parts.join(' · ');
+});
+// 与 diff 的关系：有修改 → "已修改 N 处"；0 修改 → "样本已满足该刊要求，无需修改"
+const rulesStatusText = computed(() => {
+  if (modifiedCount.value > 0) return `已修改 ${modifiedCount.value} 处`;
+  return '样本已满足该刊要求，无需修改';
+});
 // ISO 时间戳 → "10-12 15:25"（内部字段不裸露；helper 规则见 UI 注释）
 const generatedShort = computed(() => {
   const s = meta.value?.generated_at;
@@ -266,6 +291,11 @@ function download() {
           复制任务 ID
         </button>
       </div>
+      <!-- 目标期刊规则摘要：diff=0 时也能看到"该刊要求什么"（次级文字，不抢 diff 主视觉） -->
+      <p v-if="rulesSummary" class="rf-rules" data-testid="rf-rules-summary">
+        📋 该刊规则：{{ rulesSummary }}
+        <span class="rf-rules-status">（{{ rulesStatusText }}）</span>
+      </p>
       <p v-if="meta?.rules_note" class="rf-note" role="note">{{ meta.rules_note }}</p>
 
       <!-- 汇总：已修改 / 建议（橙，不计入修改）/ 结构提示 -->
@@ -540,6 +570,15 @@ function download() {
   font-size: 12.5px;
   color: var(--pa-ink-muted);
 }
+/* 规则摘要：次级文字（同 rf-meta 色阶），与汇总条的计数视觉区分 */
+.rf-rules {
+  margin: 4px 0 0;
+  font-size: 12.5px;
+  color: var(--pa-ink-muted);
+}
+.rf-rules-status {
+  color: var(--pa-ink-subtle);
+}
 .rf-copy-id {
   margin-left: 8px;
   padding: 1px 8px;