Halcyon Symbios: no tank pressure / transmitter data from BLE import

[shaheinm]

Problem

Dives imported from the Halcyon Symbios via BLE are missing tank pressure / transmitter data. The depth profile chart shows no tank overlay, and no gas consumed data is available.

Likely Cause

This is probably related to #121 (Halcyon Symbios reports 0 gas mixes). If libdivecomputer's Halcyon parser doesn't parse gas mixes, it likely also doesn't emit DC_SAMPLE_PRESSURE events for tank pressure data.

Investigation Needed

1. Check if the Halcyon BLE data blob contains transmitter data at all (it may not — depends on whether a Halcyon transmitter was paired)
2. Check if libdivecomputer's Halcyon parser supports DC_SAMPLE_PRESSURE / DC_FIELD_TANK
3. If the data exists but isn't parsed, this may need an upstream libdivecomputer fix (or a workaround in our parser layer)

Context

• Halcyon Symbios BLE support was added in Add Halcyon Symbios BLE dive computer support #118
• Gas mix parsing is already known to be broken (Halcyon Symbios reports Air instead of actual gas mix (Nx32) #121 — reports "Air" instead of actual gas)
• This may be a broader issue with the Halcyon parser in libdivecomputer