Rewrite "Final Energy|*" IAMC variables

[khaeru]

This PR will address:

• Bump fixed versions of solved MESSAGEix-Transport scenarios used in method 'C' to retrieve the aviation share of transport final energy.

  This is per @r-aneeque's list at https://iiasa-ece.slack.com/archives/CCFHDNA6P/p1747301149034789.

• Expand .ssp.transport to rewrite "Final Energy|*" variables #308

How to review

• Read the diff.
• Note that the CI checks all pass.
• Check the results of using the updated code in the SSP/ScenarioMIP workflow.

PR checklist

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

[codecov]

Codecov Report

Attention: Patch coverage is 97.91667% with 1 line in your changes missing coverage. Please review.

Project coverage is 72.0%. Comparing base (c8ab04d) to head (e8e213c).

Files with missing lines	Patch %	Lines
message_ix_models/project/ssp/transport.py	97.0%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #355   +/-   ##
=====================================
  Coverage   72.0%   72.0%           
=====================================
  Files        243     243           
  Lines      19451   19474   +23     
=====================================
+ Hits       14011   14035   +24     
+ Misses      5440    5439    -1     

Files with missing lines	Coverage Δ
...sage_ix_models/tests/project/ssp/test_transport.py	100.0% <100.0%> (+2.0%)	⬆️
message_ix_models/project/ssp/transport.py	96.2% <97.0%> (+0.3%)	⬆️

... and 1 file with indirect coverage changes

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