v0.11.11: 彻底移除技能系统，工具 44→42，SQLite 7→6 张表

- 删除 src/renderer/services/skill-manager.ts (480行)
- sqlite.ts: 删除 skills 表/索引/迁移/SkillRow接口/CRUD
- ipc.ts: 删除 6 个 skills IPC handler
- preload.ts/types.d.ts: 删除 skills bridge 方法/类型
- agent-engine.ts: 删除技能匹配上下文注入/自动提取
- tool-registry.ts: 删除 skill_list/skill_view 工具定义/执行
- log-service.ts/sub-agent.ts/workspace-panel.ts: 清理引用
- index.html: 帮助面板/工具卡片更新，44→42
- README/release-notes/DEVELOPMENT/AGENT: 文档全量同步

src/renderer/types.d.ts

@@ -462,13 +462,7 @@ export interface DBAPI {
   getTraces: (sessionId: string) => Promise<TraceEntry[]>;
   exportSessions: () => Promise<unknown>;
   importSessions: (data: unknown) => Promise<{ imported: number; skipped: number }>;
-  // v4.2 Skills
-  saveSkill: (skill: unknown) => Promise<{ success: boolean; id?: string; error?: string }>;
-  getAllSkills: () => Promise<unknown[]>;
-  deleteSkill: (id: string) => Promise<{ success: boolean; error?: string }>;
-  clearAllSkills: () => Promise<{ success: boolean; error?: string }>;
-  searchSkills: (query: string, limit?: number) => Promise<unknown[]>;
-  incrementSkillUsage: (id: string, success: boolean, durationMs: number) => Promise<{ success: boolean; error?: string }>;
+
   getAllTokenStats(): Promise<{
     sessions: Array<{
       session_id: string;