feat(init): add Claude Code installation and version checks

[divideby0]

Description

The ftk init command should verify that Claude Code is installed and up-to-date before proceeding with MCP server configuration.

Requirements

Installation Check

• Check if Claude Code is installed (claude --version)
• If not installed, prompt user: "Claude Code is not installed. Would you like to install it now?"
• If yes, run npm i -g @anthropic-ai/claude-code
• Verify successful installation

Version Check

• If installed, check current version against latest available version
• If outdated, prompt user: "Claude Code v{current} is installed. A newer version v{latest} is available. Would you like to upgrade?"
• If yes, run npm i -g @anthropic-ai/claude-code@latest
• Verify successful upgrade

Implementation Notes

• Should happen early in ftk init flow, before MCP server selection
• Use Deno.Command to check version: claude --version
• Fetch latest version from npm registry: https://registry.npmjs.org/@anthropic-ai/claude-code/latest
• Handle cases where npm is not installed
• Provide clear error messages if installation/upgrade fails
• Consider adding --skip-claude-check flag for CI/automated environments

Acceptance Criteria

• ftk init checks for Claude Code before proceeding
• User is prompted to install if missing
• User is prompted to upgrade if outdated
• Installation/upgrade process provides clear feedback
• Command continues gracefully if user declines
• Error handling for network issues, npm failures, etc.

[divideby0]

Additional Requirement

When --no-prompt flag is used, the Claude Code installation/version check should be skipped entirely to maintain non-interactive behavior.