Bug: ATPTREF and ROUTE missing from cdisc_dataset$adpp output

[Shaakon35]

Description

ATPTREF and ROUTE columns are not included in the cdisc_dataset$adpp output from export_cdisc(). These columns are available in the source data but are dropped during the ADPP dataset construction because they are not listed in CDISC_COLS$ADPP$Variable and are not part of grouping_vars.

Reported in #1228 (comment).

To reproduce

1. Load a dataset that contains ATPTREF and ROUTE columns
2. Run NCA and call export_cdisc() to generate CDISC datasets
3. Inspect cdisc_dataset$adpp — ATPTREF and ROUTE are missing

Expected behaviour

ATPTREF and ROUTE should be available in the adpp output, since they are used for ratio calculations (accumulation ratios, bioavailability) and are present in the source concentration/dose data.