v0.9.1 — K2 Air shows LiPo (was LiIon)

Fix

The K2 Air is a dual-channel LiPo balance charger, not a round-cell charger — same wire protocol as the Air 8, just polled on two channels. v0.9.0 fixed the slot count (6 → 2) but still routed parsing through the round-cell C4-Air enum maps. A freshly charged 1S–6S LiPo pack therefore showed up in Home Assistant as "LiIon" instead of "LiPo".

v0.9.1 groups the LiPo balance chargers (Air 8, K2 Air) in a BALANCE_CHARGER_MODELS set and routes both through the same AIR8_WORK_STATE_MAP / AIR8_BATTERY_TYPE_MAP enums, so:

• battery_type=1 → "LiPo" (was "LiIon")
• work_state=3 → "charging" (was already correct via the round-cell map, but now consistent)
• All other Air-8 enum semantics (storage / discharge / balance modes) apply to K2 Air too

Tests

Added a regression guard: two synthetic K2 Air frames must resolve to battery_type_str == "LiPo". 35/35 pytest cases green.

Upgrading

No config changes required. K2 Air owners — your chemistry sensor will switch from "LiIon" to "LiPo" on next load. If you have any automations matching on the string "LiIon" for the K2 Air, update them.

Thanks

Thanks again to @Mngnt (issue #3) for the report that uncovered both the model misidentification (fixed in v0.9.0) and this follow-on enum routing.