fix: skills 表增加 summary 列，修复渐进式技能加载数据丢失

Skill 接口包含 summary 字段且 extractSkillsFromToolRecords() 会生成摘要，
但 SQLite schema 和 saveSkill() 遗漏了该列，导致保存时 summary 丢失。
- CREATE TABLE 增加 summary TEXT DEFAULT ''
- 兼容迁移：ALTER TABLE 补充 summary 列
- saveSkill() INSERT 语句增加 summary 参数
- SkillRow 接口增加 summary 字段

src/main/db/sqlite.ts

@@ -210,6 +210,7 @@ export async function initDatabase(): Promise<SQL.Database> {
       id TEXT PRIMARY KEY,
       name TEXT NOT NULL,
       description TEXT NOT NULL,
+      summary TEXT DEFAULT '',
       trigger_keywords TEXT,
       tool_chain TEXT NOT NULL,
       success_count INTEGER DEFAULT 0,
@@ -225,6 +226,9 @@ export async function initDatabase(): Promise<SQL.Database> {
   // 兼容迁移：为已有 messages 表补充 prompt_eval_count 列（新库已有，旧库需要 ALTER）
   try { db.run('ALTER TABLE messages ADD COLUMN prompt_eval_count INTEGER'); } catch { /* 列已存在，忽略 */ }
 
+  // 兼容迁移：为已有 skills 表补充 summary 列
+  try { db.run("ALTER TABLE skills ADD COLUMN summary TEXT DEFAULT ''"); } catch { /* 列已存在，忽略 */ }
+
   // 尝试创建 FTS5 全文搜索（可选，sql.js 默认 WASM 可能不包含 FTS5）
   try {
     db.run(`
@@ -312,6 +316,7 @@ export interface SkillRow {
   id: string;
   name: string;
   description: string;
+  summary: string;
   trigger_keywords: string | null;
   tool_chain: string;
   success_count: number;
@@ -522,9 +527,9 @@ export function getTracesBySession(sessionId: string): TraceRow[] {
 // ─── Skills CRUD (v4.2) ───
 
 export function saveSkill(skill: SkillRow): string {
-  runExec(getDb(), `INSERT OR REPLACE INTO skills (id, name, description, trigger_keywords, tool_chain, success_count, fail_count, avg_duration_ms, created_at, updated_at, last_used_at)
-    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
-    [skill.id, skill.name, skill.description, skill.trigger_keywords, skill.tool_chain,
+  runExec(getDb(), `INSERT OR REPLACE INTO skills (id, name, description, summary, trigger_keywords, tool_chain, success_count, fail_count, avg_duration_ms, created_at, updated_at, last_used_at)
+    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+    [skill.id, skill.name, skill.description, skill.summary || '', skill.trigger_keywords, skill.tool_chain,
      skill.success_count, skill.fail_count, skill.avg_duration_ms,
      skill.created_at, skill.updated_at, skill.last_used_at]
   );