0.84.0

This release adds `--device-id`, one option that picks the device a run uses on Android, iOS simulators and physical iPhones alike, and replaces the iOS-only `--ios-real-device-id`.

## `--device-id` Selects the Device on Every OS (#447)

Until now a run took whatever single device it found, and there was no way to name one:

```bash
arbigent run --device-id=emulator-5554                       # adb serial
arbigent run --os=ios --device-id=00008110-XXXXXXXXXXXXXXXX  # simulator or iPhone UDID
```

It can also come from `ARBIGENT_DEVICE_ID` or the `device-id` settings key, with the usual precedence: flag > environment variable > settings file. Every run logs which device it picked and where the id came from.

The value is matched exactly and Arbigent never falls back to another device when the requested one is missing — running against a different device than the one you named is the failure this option exists to prevent. When several devices are connected and none was requested, that is an error listing the candidates rather than a guess, since discovery order is not stable. A device that adb reports as `unauthorized` or `offline` is listed as attached but is never selected and never counts as an ambiguity, so an unaccepted USB-debugging prompt no longer hides a working emulator. Android discovery now goes through `adb devices` instead of enumerating every device, which also stops one unauthorized phone from taking down a run aimed at another.

**Breaking change.** `--ios-real-device-id`, the `ios-real-device-id` settings key and `ARBIGENT_IOS_REAL_DEVICE_ID` are removed. Move the UDID to `--device-id` / `device-id` / `ARBIGENT_DEVICE_ID`; a leftover value is reported as a migration error rather than silently ignored.

A physical iPhone's hardware UDID is treated as sensitive: it is masked in `--help` output and never printed in full by Arbigent's own logs and errors. adb serials and simulator UDIDs are printed in full so they can be pasted straight into `--device-id`.

## What's Changed
* Add --device-id to select the device a run uses on every OS by @takahirom in https://github.com/takahirom/arbigent/pull/447


**Full Changelog**: https://github.com/takahirom/arbigent/compare/0.83.0...0.84.0