Add Apple environment install API (`maui apple install`)

[rmarinho]

Summary

Add a library API for one-shot Apple development environment installation, supporting the maui apple install command from the CLI spec.

Command to Support

Command	Description
maui apple install	Install Xcode Command Line Tools + a compatible iOS simulator runtime

Requirements

• Detect if Xcode CLT is installed; if not, trigger installation (xcode-select --install or headless approach)
• Detect if a compatible iOS simulator runtime is available; if not, install it
• Orchestrate the full flow: CLT → runtime check → runtime install
• Report progress for each step (type: "progress" JSON messages)
• Support --dry-run to preview what would be installed
• Handle cases where Xcode is present but CLT is not, and vice versa

Design Notes

• This is a high-level orchestration command that composes the lower-level APIs from the check, xcode, and runtime issues
• Should be idempotent — running when everything is already installed is a no-op
• Must handle interactive prompts (CLT installation shows a macOS dialog) and non-interactive CI environments
• Depends on: Add Apple environment check API (maui apple check) #148 (environment check), Add simulator management APIs (maui apple simulator) #149 (Xcode management), Add Xcode management APIs (maui apple xcode list, select) #151 (runtime management)

Reference

• CLI spec PR