feat(skiff): replace opencode target with agents standard dir

- targets: cursor, claude, codex, agents (~/.agents/skills, .agents/skills)
- agents dir covers OMP native discovery; drop omp/opencode targets
- project-level agents/cursor/codex share .agents/skills via idempotent symlinks
- migrate local state: remove ~/.config/opencode/skills links, reinstall into ~/.agents/skills

skiff/README.md

@@ -58,7 +58,7 @@ skiff bootstrap
 | 命令 | 说明 |
 |------|------|
 | `skiff list [--source NAME]` | 列出所有来源或指定 source 中的 skill |
-| `skiff status [--target all\|cursor\|claude\|codex]` | 安装状态总览 |
+| `skiff status [--target all\|cursor\|claude\|codex\|agents]` | 安装状态总览 |
 
 ### 项目初始化
 
@@ -87,6 +87,7 @@ skiff bootstrap
 | cursor | `~/.cursor/skills/` |
 | claude | `~/.claude/skills/` |
 | codex | `~/.codex/skills/` |
+| agents | `~/.agents/skills/`（agents 标准目录，覆盖 OMP） |
 
 ### 预置 Catalog Source
 
@@ -171,6 +172,7 @@ skiff 不保存 token。可以使用 `company/code-review`，也可以使用
 | cursor | `<project>/.agents/skills/` |
 | claude | `<project>/.claude/skills/` |
 | codex | `<project>/.agents/skills/` |
+| agents | `<project>/.agents/skills/`（与 cursor/codex 共用路径，软链幂等） |
 
 ### 脚手架与健康检查