formats/json-payload.md: full rewrite around the actual server-side template
(endpoint api.aircarto.com/receive_data?device_type=<model>, flat schema,
_unit suffix companions, -1 and 255 sentinel semantics, full bitfield
tables for error_flags/npm_status/device_status, misc context codes).
formats/iso-pollutant-codes.md: fill in the LCSQA mapping. Fixes my earlier
inversion — ISO_39=PM2.5 and ISO_24=PM10 (not the other way). Add gases:
ISO_03=NO2, ISO_04=CO, ISO_05=H2S, ISO_08=O3, ISO_21=NH3.
parsers/udp-miotiq.md:
- string base function outputs hex (not ASCII) — update description and
generic Python parser accordingly.
- Fix ISO_39/ISO_24 labels in NebuleAir Pro 4G byte layout.
- Name the 5 gases by offset, cross-link bitfield docs and JSON canonical.
- New TODO: origin of latitude/longitude/misc in final JSON (not in 83B
descriptor).
README.md: reflect the new file layout and data flow summary.
- Refactor parsers/udp-miotiq.md around the pipe-separated descriptor format used on Miotiq side.
- Document the full 83-byte NebuleAir Pro 4G descriptor (PM, gases, noise, weather, power, status).
- Keep legacy MobileAir 17B binary format for reference.
- Add formats/iso-pollutant-codes.md placeholder for AirCarto ISO 7168 code mapping.
- Open TODOs: flag W semantics, endianness, signed battery_current, MobileAir migration.
