feat: add self-update command with automatic migrations

[sanchxt]

Summary

Implements the yoop update command to enable seamless self-updating directly from the CLI without manual npm commands.

Features

• Self-update command: yoop update handles version checking, downloading, and installation
• Automatic update checks: Background checks during long-running commands (share, receive, clipboard)
• Migration framework: Automatic config/data migration when schema changes between versions
• Backup and rollback: Full backup before updates with yoop update --rollback support
• Package manager detection: Auto-detects and uses npm/pnpm/yarn/bun
• Multiple output modes: Normal, JSON (--json), and quiet (--quiet) output

Commands

yoop update                    # Update to latest version
yoop update --check            # Check for updates without installing
yoop update --rollback         # Rollback to previous version
yoop update --force            # Force reinstall current version
yoop update --package-manager pnpm  # Use specific package manager

Configuration

New [update] section in config.toml:

[update]
auto_check = true              # Enable background update checks
check_interval = "24h"         # Interval between checks
package_manager = null         # Auto-detect if not set
notify = true                  # Show update notifications

Implementation Details

• Version checking: Queries npm registry API with caching to respect check_interval
• Migration system: Trait-based migrations with up/down support for schema changes
• Backup manager: Automatic backups before updates, keeps last 5, stored in platform data directory
• Package manager detection: Priority: CLI flag → config → env var → auto-detect → fallback to npm

Testing

• 47 tests passing (36 unit + 11 integration)
• Full coverage of version parsing, package manager detection, backup/restore, migrations, and update workflow
• Verified on Linux with all package managers