refactor: remove container references from setup, use host process runners

- setup/container.ts: replace container build with npm run build:runners
- setup/index.ts: rename step container → runners
- setup/environment.ts: remove Docker/Apple Container detection
- setup/service.ts: remove Docker group stale check, add nodeBin and
  npm-global to service PATH for codex CLI
- setup/verify.ts: remove container runtime check
- SKILL.md: rewrite for container-free setup, add Codex auth step

setup/index.ts

@@ -10,7 +10,7 @@ const STEPS: Record<
   () => Promise<{ run: (args: string[]) => Promise<void> }>
 > = {
   environment: () => import('./environment.js'),
-  container: () => import('./container.js'),
+  runners: () => import('./container.js'),
   groups: () => import('./groups.js'),
   register: () => import('./register.js'),
   mounts: () => import('./mounts.js'),