Variable naming when combining different level types in one dataset

[mpartio]

Describe the bug

When combining surface level and pressure level data in a single dataset, the naming convention is param_level which is silly for certain surface level parameters that already have the level information in their name (for example 2t).

To Reproduce

dates:
  start: 2024-10-12T14:00:00Z
  end: 2024-10-12T14:00:00Z
  frequency: 1h
input:
  join:
  - grib:
      path: example.grib2
      param: [2t]
      levtype: sfc
  - grib:
      path: example.grib2
      param: [z]
      levtype: pl
      levelist: [1000]

$ anemoi-datasets create example.yaml example.zarr

$ anemoi-datasets inspect example.zarr
📦 Path          : example.zarr
🔢 Format version: 0.30.0

📅 Start      : 2024-10-12 14:00
📅 End        : 2024-10-12 14:00
⏰ Frequency  : 1h
🚫 Missing    : 0
🌎 Resolution : 2p5km
🌎 Field shape: [1069, 949]

📐 Shape      : 1 × 2 × 1 × 1,014,481 (7.7 MiB)
💽 Size       : 13.4 MiB (13.4 MiB)
📁 Files      : 75

   Index │ Variable │     Min │     Max │    Mean │   Stdev
   ──────┼──────────┼─────────┼─────────┼─────────┼────────
       0 │ 2t_2     │ 262.871 │ 289.308 │ 280.725 │ 3.92529
       1 │ z_1000   │ -2214.4 │ 1830.41 │ 485.131 │ 977.196
   ──────┴──────────┴─────────┴─────────┴─────────┴────────
🔋 Dataset ready, last update 3 hours ago.
📊 Statistics ready.

URL to sample input data

Attached to this issue ticket.

Expected behavior

surface level parameters are without level value, ie. "2t"
vertical levels (pressure, hybrid, whatever) are with level value, ie "z_1000"

Additional context

$ anemoi-datasets --version
0.5.7

I tried changing "variable_naming" in "build":

build:
    variable_naming: param

But this changed the naming for all sources -- I need to change the naming for just a single source.

[mpartio]

example.grib2.gz

example data -- compressed with gzip because github did not allow uploading of grib.