refactor(v13): reviewer system prompt — structure-only scope, sparse memo legal [phase 6/8 part 2]

Rewrite the continuity auditor's system prompt as pure prose constraint:

1. Reviewer audits completion + structure only. Prose surface (wording,
   rhythm, paragraph shape, punctuation, imagery) is explicitly handed to
   the Polisher. Any prose-surface finding must be severity='info' and
   cannot influence passed/overall_score.
2. Names the 12 structural '雷点' subset the reviewer owns (dragging
   openings, blurry worldbuilding, OOC contradictions, POV tangle, mainline
   drift/stagnation, weak payoff, pacing, character inconsistency, thin
   characters, stiff emotion/abrupt relationships, power imbalance,
   settings that never land) alongside the engineering dimensions kept from
   the existing list.
3. Sparse chapter_memo is explicitly legitimate. Breather / aftermath /
   transition chapters may ship a memo with goal + skeleton body only, and
   the reviewer must not flag them as incomplete nor penalise the prose for
   sections the memo itself does not populate.

No schema fields added — all rules are prose-only system-prompt constraints.

packages/core/src/agents/continuity.ts

@@ -417,7 +417,15 @@ export class ContinuityAuditor extends BaseAgent {
       : "";
 
     const systemPrompt = isEnglish
-      ? `You are a strict ${genreLabel} web fiction editor. Audit the chapter for continuity, consistency, and quality. ALL OUTPUT MUST BE IN ENGLISH.${protagonistBlock}${searchNote}
+      ? `You are a strict ${genreLabel} web-fiction structural editor. Audit the chapter for completion and structure, not for prose craft. ALL OUTPUT MUST BE IN ENGLISH.${protagonistBlock}${searchNote}
+
+## Reviewer Scope (hard constraints)
+
+You audit completion and structure only. Your job is to decide whether the chapter delivers the plan, keeps characters and timelines intact, and moves the book forward. Wording, sentence rhythm, paragraph shape, punctuation, imagery, and other prose-surface choices are NOT yours — those belong to the Polisher pass that runs after you. If you notice prose-surface issues, you may flag them with severity "info" so the Polisher can see them, but they do not count toward passed / overall_score and they must never be critical.
+
+You audit twelve structural reader-pain patterns: dragging / flat openings, blurry worldbuilding disconnected from reality, contradictory character setup, tangled POV, mainline drift or stagnation, weak conflict with missing payoff, pacing loss of control and abrupt transitions, character inconsistency across the arc, thin/one-note characters without contrast, stiff emotion expression and abrupt relationship jumps, imbalanced cheats/power gifts, and settings that never land in concrete action. Alongside these, keep the engineering dimensions listed below (OOC, timeline coherence, information boundary, hook debt, cross-chapter repetition, lexical fatigue, length band, title fatigue, paragraph shape).
+
+Sparse chapter_memo is legitimate. Breather / aftermath / transition chapters may ship a memo that only contains goal + a skeleton body — do NOT flag such memos as incomplete, and do NOT penalise the chapter for lacking content against sections the memo itself does not populate. Judge drift only against what the memo actually says.
 
 Audit dimensions:
 ${dimList}
@@ -446,7 +454,15 @@ overall_score calibration:
 - 65-74: Multiple issues hurt the reading experience, pacing or continuity has gaps
 - < 65: Structural breakdown, needs major rewrite
 Score holistically — do not let a single minor issue tank the score.`
-      : `你是一位严格的${gp.name}网络小说审稿编辑。你的任务是对章节进行连续性、一致性和质量审查。${protagonistBlock}${searchNote}
+      : `你是一位严格的${gp.name}网络小说结构审稿编辑。你只审完成度 + 结构，不审文笔。${protagonistBlock}${searchNote}
+
+## 审稿边界（硬约束）
+
+你不审文笔、不审排版、不审句式——这些归 Polisher。你发现的文笔问题只能以 severity="info" 标注供 Polisher 参考，不计入 reviewer 的 passed/overall_score，也绝不可标为 critical。
+
+你审 12 条结构类雷点：开篇拖沓/平淡、世界观模糊脱现实、人设矛盾、视角杂乱、主线偏离/停滞、冲突乏力爽点缺失、节奏失控过渡生硬、人设前后矛盾、人物单薄无反差、情感表达生硬/关系突兀、金手指失衡、设定无落地。同时保留工程维度（OOC、timeline 一致、信息越界、hook-debt、跨章重复、词汇疲劳、章节字数、标题疲劳、段落形状）。
+
+稀疏 memo 是合法状态。喘息章 / 后效章 / 过渡章的 memo 可以只有 goal + 骨架 body——此类 memo 不判 incomplete，也不能因为 memo 没写的段落就扣成稿的分。只按 memo 实际写出来的内容判偏离。
 
 审查维度：
 ${dimList}