feat: --beta skills — pre-install MCP servers and skills on VMs (#3258)

CLI plumbing for the skills feature. The skills catalog in manifest.json
is populated by the discovery scout (#3252), not manually curated.

Flow:
1. User runs `spawn claude hetzner --beta skills`
2. Skills picker shows available skills for that agent (from manifest.json)
3. User selects skills, enters required env vars (GITHUB_TOKEN, etc.)
4. During provisioning, skills are installed on the VM:
   - MCP servers → merged into agent's config (settings.json, mcp.json)
   - Instruction skills → SKILL.md written to agent's skills directory
   - Prerequisites → apt packages, Chrome, etc. installed first
5. Env vars appended to .spawnrc for MCP server runtime access

Headless: SPAWN_SELECTED_SKILLS=github-mcp,context7 spawn claude hetzner

Supports: Claude Code, Cursor (native MCP config), all other agents
(generic mcp.json fallback).

Signed-off-by: Ahmed Abushagur <ahmed@abushagur.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openrouter/spawn",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "type": "module",
   "bin": {
     "spawn": "cli.js"