fix(printers): don't retract a fan kit on a partial airduct frame

device.airduct is pushed field by field - the modeCur handler reads it with
an "in" check for that reason - so a frame can carry parts without carrying
every fan. Absence in that list is what tells us a kit is not fitted, and
taken from a truncated frame it made both accessory badges vanish mid-print
and started rejecting fan=aux2 on a printer that has the fan.

A parts list now counts as a full inventory only when it carries ids 1 (part
cooling) and 2 (aux). Neither is optional on a machine that reports an
airduct at all, and both appear in every layout in the support-package
archive - P2S base 1,2 / P2S+kit 1,2,3 / X2D 1,2,3,10 / H2C,H2D,H2S 1,2,3,6.
Anything narrower is a diff frame: its speeds are applied, presence is left
alone. Presence can still be added from a partial frame; only retraction
needs the full list, so a kit that really is removed still disappears.

Also compose showChamberFan from both model lists rather than branching
between them, so the P2S/X2D entries in MODELS_WITH_CHAMBER_FAN stay
reachable instead of reading as dead, and note in the fan-speed docstring
that the aux2 gate also rejects between connect and the first airduct push.

frontend/src/pages/PrintersPage.tsx

@@ -3908,7 +3908,13 @@ function PrinterCard({
               const chamberFanLabel = isExhaustModel
                 ? t('printers.fans.exhaust')
                 : t('printers.fans.chamber');
-              const showChamberFan = isExhaustModel ? status.exhaust_fan_present : hasChamberFan;
+              // Composed rather than either/or so both lists stay live for
+              // P2S/X2D: the model must have an enclosure fan at all, AND —
+              // where that fan is an add-on kit — actually report it. Written
+              // as `isExhaustModel ? exhaust_fan_present : hasChamberFan` the
+              // P2S/X2D entries in MODELS_WITH_CHAMBER_FAN became unreachable,
+              // which reads as if removing them were safe.
+              const showChamberFan = hasChamberFan && (!isExhaustModel || status.exhaust_fan_present);
               const fanItems: {
                 key: string;
                 label: string;