Also fixes a live bug found while refactoring: buildEscPos returned a
Uint8Array, but its caller in printThermalBluetooth() ran the result
through TextEncoder.encode() (which expects a string) before writing
to the Bluetooth characteristic — encoding a Uint8Array's default
toString() ("27,64,27,...") instead of the actual bytes. Regular
(non-account) sale slips printed over Bluetooth have been sending
garbled data. Both builders now return plain strings, matching
buildEscPosDelivery's already-correct pattern.
Also preserves a pre-existing divergence rather than silently
resolving it: Bluetooth's delivery note prints letterhead business
info (name/address/phone/VAT), the network XML version never has.
Kept as-is per transport (folded into Bluetooth's header_title block)
rather than unilaterally adding or removing content — worth an
explicit decision later on which behavior is correct.
Dave
f07d70b976