* feat(cli): support slash commands from installed plugins
Allows HAPI to automatically scan and load slash commands from installed Claude plugins (e.g. superpowers). Commands are indexed with their plugin namespace prefix.
* fix(web): add 'plugin' to SlashCommand source type
This fixes the typecheck error identified by the PR review bot.
* fix(web): update Suggestion type to include 'plugin' source
* fix(slashCommands): 修复 scoped 插件名称解析及多版本安装选择逻辑
- 使用 lastIndexOf('@') 替代 split('@')[0] 以正确解析带 scope 的插件名
- 按 lastUpdated 降序排序选择最新的安装实例
- 增加 installations 空数组边界检查
