Add non-blocking update check that queries the npm registry for the
latest @larksuite/cli version. Results are cached locally (24h TTL)
to avoid repeated network requests.
When a newer version is detected, a `_notice.update` field is injected
into all JSON output envelopes (success, error, and shortcut responses),
enabling AI agents and scripts to surface upgrade prompts.
Key changes:
- New `internal/update` package: registry fetch, semver compare, cache
- Async check in root command (cache-first, then background refresh)
- `_notice` field added to Envelope/ErrorEnvelope structs
- `PrintJson` injects notice into map-based envelopes with "ok" key
- `doctor` command gains cli_version and cli_update checks
- Suppressed for CI, DEV builds, shell completion, and git-describe versions
