fix: add nvm install step before npm install in Quick Start

[amanbuild]

Problem

Running npm install -g @openacp/cli directly fails on systems where Node.js is not installed or managed via nvm, because npm is not available.

The current Quick Start guide assumes Node.js is already installed, which is not always the case — especially on fresh Linux/macOS environments.

Suggested Fix

Add nvm installation before the npm step:

# 1. Install nvm
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash

# 2. Load nvm (add to .bashrc / .zshrc)
export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"

# 3. Install Node.js LTS
nvm install --lts
nvm use --lts

# 4. Then install OpenACP
npm install -g @openacp/cli
openacp

Context

The OpenClaw install script (curl -fsSL https://openclaw.ai/install.sh | bash) handles Node.js installation automatically — OpenACP Quick Start should do the same or at minimum document the nvm prerequisite.

Affected

• README Quick Start section
• Docs quick start page