What changed

Fixed AirPods appearing as two device cards for ~10–20 seconds when taking them out of the case. The duplicate showed wrong battery values and disappeared again on its own.

Closes #603

Technical Context

• Root cause: on connect, AirPods Gen 4 emit a single proximity-pairing frame from their identity address whose payload prefix is 0x07 instead of 0x01. The model bytes happen to sit at the usual offset so it passed model matching, but the rest of the payload is not the plaintext status format (battery nibbles 13/14, invalid color) — it minted a fresh device tracker that matched the same profile and rendered as a second card until the 20 s stale timeout.
• The guard sits at the decoder layer, before model dispatch, so every model — including the unknown-device catch-all — is protected; per-model validation would have left the catch-all exposed.
• Safe for pairing mode and clones: every real-device capture in the test suite (all AirPods, Beats, and fake variants) uses prefix 0x01, and pairing/connection state is encoded in the payload suffix byte, not the prefix.
• Dropped frames are still logged with their full hex payload at DEBUG, so unrecognized variants stay visible in user debug logs.