fix: skip unavailable devices during adb-server enumeration

[PointBreaker]

Problem

host:devices includes each transport's state, but listDadbs() currently discards it and constructs a Dadb for every serial. Constructing an unauthorized or offline transport throws during the feature query and aborts the whole list, hiding healthy devices on the same host.

This was reproduced through Maestro with a healthy requested device remaining continuously available to adb while dadb-based discovery reported no connected Android devices.

Change

• Only construct connections for entries in the device state.
• Isolate an IOException from one entry so a transport race cannot hide the other healthy devices.
• Keep AdbServerDadb initialization and connection behavior unchanged.

Testing

• ./gradlew :dadb:test --tests dadb.adbserver.AdbServerDeviceListTest

Fixes #55
Fixes #62

Related to #98 and mobile-dev-inc/Maestro#3456.