feat(frontend): 编辑器内「润色 / 再沟通」——选段回炉 + 追加意见迭代出版本栈，接受回填

Phase 1（写作工作台重构）：编辑器选中一段即可「润色选段」，复用同步 /refine 回炉
（只读、不写库，守不变量 #3）；不满意可「再沟通」——以上一版产出为输入 + 作者新意见
再改一版，形成版本栈（useRefine，已单测）。接受回填按内容重锚落回草稿，原文已变则
提示重选、绝不盲替换（applyRefinement，已单测）。Editor 上报选区，结果以内联卡片展示。

apps/web/components/workbench/RefinePanel.tsx

@@ -0,0 +1,133 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+import { Check, MessageSquarePlus, RotateCcw, X } from "lucide-react";
+
+import { ThinkingIndicator } from "@/components/ThinkingIndicator";
+import { Button } from "@/components/ui/Button";
+import { SectionHeader } from "@/components/ui/SectionHeader";
+import { StatusNote } from "@/components/ui/StatusNote";
+import { TextArea } from "@/components/ui/TextArea";
+import { useRefine } from "@/lib/workbench/useRefine";
+
+interface RefinePanelProps {
+  projectId: string;
+  chapterNo: number;
+  // 选中原文；打开即对其回炉一次。
+  original: string;
+  // 接受回填：把选段替换为该产出（调用方按内容重锚落回草稿）。
+  onAccept: (refined: string) => void;
+  onClose: () => void;
+}
+
+// 润色 / 再沟通结果卡（内联，非模态）：打开即润色选段；作者可「再沟通」追加意见迭代出新版，
+// 择版接受回填正文，或放弃。原文只读、生成不写库（不变量 #3），accept 才动草稿。
+export function RefinePanel({
+  projectId,
+  chapterNo,
+  original,
+  onAccept,
+  onClose,
+}: RefinePanelProps) {
+  const { status, versions, latest, refine, recommunicate } = useRefine();
+  const [instruction, setInstruction] = useState("");
+  const ranRef = useRef(false);
+
+  // 打开即对选段回炉一次（仅一次，避免重复请求）。
+  useEffect(() => {
+    if (ranRef.current) return;
+    ranRef.current = true;
+    void refine(projectId, chapterNo, original);
+  }, [projectId, chapterNo, original, refine]);
+
+  const busy = status === "refining";
+
+  const onRecommunicate = (): void => {
+    const trimmed = instruction.trim();
+    if (!trimmed || busy) return;
+    setInstruction("");
+    void recommunicate(projectId, chapterNo, trimmed);
+  };
+
+  return (
+    <div className="border-b border-line bg-panel px-4 py-3 sm:px-6">
+      <div className="flex items-center justify-between gap-3">
+        <SectionHeader
+          title="润色 / 再沟通"
+          description="对选中段回炉；不满意可追加意见让 AI 再改一版，满意后接受回填。"
+        />
+        <Button onClick={onClose} variant="ghost" size="icon" aria-label="关闭润色">
+          <X className="h-4 w-4" aria-hidden="true" />
+        </Button>
+      </div>
+
+      <div className="mt-3 grid gap-3 sm:grid-cols-2">
+        <figure className="rounded border border-line bg-bg p-3">
+          <figcaption className="mb-1 text-2xs text-ink-soft">原文</figcaption>
+          <p className="whitespace-pre-wrap text-sm text-ink-soft">{original}</p>
+        </figure>
+        <figure className="rounded border border-cinnabar/40 bg-bg p-3">
+          <figcaption className="mb-1 flex items-center gap-2 text-2xs text-ink-soft">
+            改写
+            {versions.length > 0 ? (
+              <span className="rounded bg-panel px-1.5 py-0.5 tabular-nums">
+                第 {versions.length} 版
+              </span>
+            ) : null}
+          </figcaption>
+          {busy && !latest ? (
+            <ThinkingIndicator label="润色中" className="text-xs text-cinnabar" />
+          ) : latest ? (
+            <p className="whitespace-pre-wrap text-sm text-ink">{latest.refined}</p>
+          ) : status === "error" ? (
+            <StatusNote variant="danger" className="text-xs" title="回炉失败">
+              <button
+                type="button"
+                onClick={() => void refine(projectId, chapterNo, original)}
+                className="mt-1 inline-flex items-center gap-1 text-cinnabar hover:underline"
+              >
+                <RotateCcw className="h-3.5 w-3.5" aria-hidden="true" />
+                重试
+              </button>
+            </StatusNote>
+          ) : null}
+        </figure>
+      </div>
+
+      <div className="mt-3 space-y-2">
+        <label className="block">
+          <span className="sr-only">再沟通意见</span>
+          <TextArea
+            value={instruction}
+            onChange={(e) => setInstruction(e.target.value)}
+            rows={2}
+            placeholder="再沟通：想怎么改？（如「再收紧节奏」「保留这句比喻」）"
+          />
+        </label>
+        <div className="flex flex-wrap items-center gap-2">
+          <Button
+            onClick={onRecommunicate}
+            disabled={busy || instruction.trim().length === 0}
+            variant="secondary"
+            size="sm"
+          >
+            <MessageSquarePlus className="h-4 w-4" aria-hidden="true" />
+            再改一版
+          </Button>
+          <Button
+            onClick={() => latest && onAccept(latest.refined)}
+            disabled={busy || !latest}
+            variant="primary"
+            size="sm"
+          >
+            <Check className="h-4 w-4" aria-hidden="true" />
+            接受回填
+          </Button>
+          {busy ? (
+            <ThinkingIndicator label="生成中" className="text-xs text-cinnabar" />
+          ) : null}
+        </div>
+      </div>
+    </div>
+  );
+}