chore: update `INVALID_DIRS` to include plural 'skills' directory (#6255)

packages/opencode/src/config/config.ts

@@ -155,7 +155,7 @@ export namespace Config {
     }
   })
 
-  const INVALID_DIRS = new Bun.Glob(`{${["agents", "commands", "plugins", "tools"].join(",")}}/`)
+  const INVALID_DIRS = new Bun.Glob(`{${["agents", "commands", "plugins", "tools", "skills"].join(",")}}/`)
   async function assertValid(dir: string) {
     const invalid = await Array.fromAsync(
       INVALID_DIRS.scan({