feat: cac env export/import — portable environment config

[nmhjklnm]

Summary

Export environment configuration as JSON for backup or cross-machine sync. Import on another machine to recreate the environment.

Proposed API

cac env export <name> [--config-only] > work.json
cac env import <name> --from work.json

JSON format

{
  "name": "work",
  "proxy": "socks5://u:p@host:port",
  "version": "2.1.83",
  "tz": "Asia/Shanghai",
  "lang": "en_US.UTF-8",
  "settings": { "permissions": { "defaultMode": "bypassPermissions" }, ... },
  "claude_md": "# My CLAUDE.md content..."
}

Design decisions

• Identity info (uuid, stable_id, mac, hostname, machine_id) is never exported — each machine generates its own
• --config-only: export only config (proxy, version, tz, settings) — no sessions or credentials
• Without --config-only: include .claude/ directory content (sessions, memory) for full backup
• On import: auto-generate identity, auto-install Claude Code version if not present

Use cases

1. Backup: export full environment before system reinstall
2. Multi-machine: share proxy + settings config across machines
3. Team onboarding: share a standard config file

[nmhjklnm]

Closing as no longer planned.