feat: make skills invokable as slash commands in the TUI

- Add Skill.content() method to load skill template content from SKILL.md files
- Modify Command.list() to include skills as invokable commands
- Add 'skill' boolean property to Command.Info schema
- Update autocomplete to show skills with (Skill) label in slash commands
- Regenerate SDK to include skill property in Command type

packages/opencode/src/skill/skill.ts

@@ -153,4 +153,11 @@ export namespace Skill {
   export async function all() {
     return state().then((x) => Object.values(x))
   }
+
+  export async function content(name: string) {
+    const info = await get(name)
+    if (!info) return undefined
+    const md = await ConfigMarkdown.parse(info.location)
+    return md.content
+  }
 }