fix: 自定义规则置顶生效，写入前校验策略名存在

规则首条匹配即生效，自定义规则此前插在模板规则之后、FINAL 之前，被
download.conf 等宽泛规则集抢先命中（brew.sh 配了代理仍直连）。现在新建
规则插到 seq 0，重新播种时也把自定义规则整体排在模板规则之前。

同时把 BUILTIN_POLICIES 提到 shared 共用，规则新建／编辑时校验策略必须是
内置策略或已有策略组，避免引用不存在的策略被 IR 静默剔除；前端表单默认
策略由不存在的「Proxy」改为 DIRECT。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/routes/rules.ts

@@ -1,11 +1,11 @@
 import { Hono } from 'hono';
 import { zValidator } from '@hono/zod-validator';
-import { asc, eq } from 'drizzle-orm';
+import { asc, eq, sql } from 'drizzle-orm';
 import { nanoid } from 'nanoid';
 import { z } from 'zod';
-import { ruleInputSchema, type RuleDto } from '@proxy-station/shared';
+import { BUILTIN_POLICIES, ruleInputSchema, type RuleDto } from '@proxy-station/shared';
 import { db } from '../db/index.js';
-import { rules, rulesets } from '../db/schema.js';
+import { policyGroups, rules, rulesets } from '../db/schema.js';
 import { seedRulesFromTemplate } from '../db/seed.js';
 
 function loadRules(): RuleDto[] {
@@ -22,29 +22,26 @@ function loadRules(): RuleDto[] {
   });
 }
 
-function nextSeq(): number {
-  const rows = db.select({ seq: rules.seq }).from(rules).all();
-  return rows.length ? Math.max(...rows.map((r) => r.seq)) + 1 : 0;
+/** 引用不存在的策略组会被 IR 静默剔除，必须在写入前拦下 */
+function policyError(policy: string): string | null {
+  if ((BUILTIN_POLICIES as readonly string[]).includes(policy)) return null;
+  const exists = db.select({ id: policyGroups.id }).from(policyGroups).where(eq(policyGroups.name, policy)).get();
+  return exists ? null : `策略「${policy}」不存在：请选择内置策略或已有策略组`;
 }
 
 export const rulesRoute = new Hono()
   .get('/', (c) => c.json(loadRules()))
   .post('/', zValidator('json', ruleInputSchema), (c) => {
     const input = c.req.valid('json');
-    // 新自定义规则插到 FINAL 之前
-    const finalRow = db.select().from(rules).where(eq(rules.type, 'FINAL')).get();
-    let seq: number;
-    if (finalRow) {
-      seq = finalRow.seq;
-      db.update(rules).set({ seq: finalRow.seq + 1 }).where(eq(rules.id, finalRow.id)).run();
-    } else {
-      seq = nextSeq();
-    }
+    const err = policyError(input.policy);
+    if (err) return c.json({ error: err }, 400);
+    // 规则首条匹配即生效，自定义规则必须压过模板里的宽泛规则集（如 download.conf），插到最前
+    db.update(rules).set({ seq: sql`${rules.seq} + 1` }).run();
     const id = nanoid(10);
     db.insert(rules)
       .values({
         id,
-        seq,
+        seq: 0,
         type: input.type,
         value: input.value ?? null,
         policy: input.policy,
@@ -69,6 +66,8 @@ export const rulesRoute = new Hono()
     const existing = db.select().from(rules).where(eq(rules.id, id)).get();
     if (!existing) return c.json({ error: '规则不存在' }, 404);
     const input = c.req.valid('json');
+    const err = policyError(input.policy);
+    if (err) return c.json({ error: err }, 400);
     db.update(rules)
       .set({
         type: input.type,