Transport improvements for 2024-W36

[khaeru]

• [ ] Postprocess SSP 2024 reporting output to compute aviation emissions.
  • [x] Initial implementation using a fixed share of total transportation emissions.
  • [ ] Compute absolute emissions using:
    • Emission factors from GAINS, at the highest possible resolution.
    • Aviation share of total transport final energy, computed using latest IEA EWEB data.
• [x] Add transport mode F RAIL with two technologies.
• [x] Add a technology for F ROAD that consumes commodity=electr.
• [x] Add "SSP1-LED", "SSP2-LED", "EDITS-CA", "EDITS-HA" scenarios to transport workflow.
  • For LED: replace PDT per capita (with mode dimension) from Schafer logic with values computed based on LED narrative; this is then multiplied by SSP-specific population.
  • For EDITS: replace PDT (absolute/not per-capita; with mode dimension) aggregated from ITF data. No multiplication is needed.
• [ ] #229
• [ ] #230

Housekeeping:

• Add a emission code list.

How to review

• Read the diff and note that the CI checks all pass.
• View the preview build of the docs.
• Run the command described here and confirm (a) it works and (b) the output is as desired.

PR checklist

• [ ] Continuous integration checks all ✅
• [ ] Add or expand tests; coverage checks both ✅
• [ ] Add, expand, or update documentation.
• [ ] Update doc/whatsnew.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 59.5%. Comparing base (7c50871) to head (9dc84fe). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #225 +/- ## ===================================== Coverage 59.5% 59.5% ===================================== Files 195 195 Lines 15491 15491 ===================================== Hits 9225 9225 Misses 6266 6266 ```