Review follow-up on the v2 -> v3 migration.
`new_unit_class` only exists from HA 2025.11, but hacs.json still declares
2025.1 as the minimum. On anything in between, naming that keyword is a
TypeError raised out of async_migrate_entry, which fails the config entry
outright -- the integration would not load at all for those users. The
keyword is now feature-detected, and the relabel is wrapped so that no
recorder-side surprise can cost anyone the integration: it is a
convenience, and without it they simply get Home Assistant's own
units_changed repair, which is where they were before this existed.
The version bump also no longer happens when the recorder wasn't loaded.
That case isn't distinguishable from an install without the recorder, but
burning the one-shot migration on a boot where it merely failed to come up
would leave the statistics suppressed permanently, so the entry stays on
v2 and the next start retries.
The instance-suffix regex was wrong: discovery.instance_suffix yields
`_<n>`, so keys are `dust_1`, not `dust1`. Unreachable today because
AIR_QUALITY binds an exact href, but the comment claimed a guarantee the
pattern didn't provide and the test pinned a form that can't occur.
Also drops a stale claim in airconditioner.py that air_monitor rejects the
pm10/pm25/pm1 mapping, which is no longer true as of this branch.
Tests cover both signatures, the deferral and its retry, and a relabel
that raises. The older-HA guard is mutation-checked: removing the feature
detection fails it.
Marc Billow
9f1bcad3ec