Bridge cache replaced prev state wholesale on each incremental, re-merging
only a 14-key allowlist. Capability/lifecycle fields (cali_version,
print_type, mc_print_stage, device, ...) drained out within one 1Hz tick,
greying out BambuStudio's Device-tab UIs (manage-calibration, AMS-slot
dropdown) once the cache thinned. Most P1S users miss it by timing — they
click Device tab while the cache is still fat from the connect pushall.
Switch to per-field accumulate matching bambu_mqtt.py's internal state
handler: prev keys carry over verbatim when not present in the incoming
push, new values overwrite when present. _merge_ams_dict for partial AMS
blobs unchanged (#1387 / #1371 regression guards stay green).
_SLICER_VISIBLE_STICKY_KEYS removed — new logic is a strict superset.