feat(ux): R1+R2 审稿裁决人体学 — 冲突卡内联片段 + 分组/排序/跳下一条/主次按钮

R1: 新 lib/review/snippet.ts 从 where 解析段号取终稿命中段预览，ConflictCard 渲染引用块。
R2: 新 lib/review/grouping.ts 按 type 分组+严重度排序（仅改显示顺序，保留原始 index 守 conflict_index 不变量），组计数徽标、跳到下一条未裁决（环回）、采纳改法主按钮/忽略手改次级。
TDD: snippet 8 测 + grouping 10 测。前端门禁绿: lint/tsc/vitest 201/build。

apps/web/lib/review/snippet.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, it } from "vitest";
+
+import { conflictSnippet, parseParagraphNo } from "./snippet";
+
+describe("parseParagraphNo", () => {
+  it("extracts 1-based paragraph number from 第 N 段 wording", () => {
+    expect(parseParagraphNo("第 3 段，主角忽然示弱")).toBe(3);
+    expect(parseParagraphNo("第9段老者道破来历")).toBe(9);
+  });
+
+  it("returns null when no paragraph number present", () => {
+    expect(parseParagraphNo("战斗场景")).toBeNull();
+    expect(parseParagraphNo("开篇提到三日后")).toBeNull();
+    expect(parseParagraphNo("")).toBeNull();
+  });
+
+  it("takes the first number for a range like 第 4–6 段", () => {
+    expect(parseParagraphNo("第 4–6 段反复描写天气")).toBe(4);
+  });
+});
+
+describe("conflictSnippet", () => {
+  const text = "第一段正文。\n\n第二段正文。\n\n第三段正文，命中冲突的句子。";
+
+  it("returns the trimmed paragraph for a parseable where", () => {
+    expect(conflictSnippet(text, "第 3 段，主角忽然示弱")).toBe(
+      "第三段正文，命中冲突的句子。",
+    );
+  });
+
+  it("returns null when paragraph number is unparseable", () => {
+    expect(conflictSnippet(text, "战斗场景")).toBeNull();
+  });
+
+  it("returns null when paragraph index is out of range", () => {
+    expect(conflictSnippet(text, "第 9 段")).toBeNull();
+  });
+
+  it("returns null when the located paragraph is empty", () => {
+    expect(conflictSnippet("\n\n\n\n正文", "第 1 段")).toBeNull();
+  });
+
+  it("truncates long paragraphs with an ellipsis", () => {
+    const long = "甲".repeat(200);
+    const snippet = conflictSnippet(long, "第 1 段");
+    expect(snippet).not.toBeNull();
+    expect(snippet!.length).toBeLessThanOrEqual(81);
+    expect(snippet!.endsWith("…")).toBe(true);
+  });
+});