Restructure core bounds

[lecfab]

Purpose of this PR

Tried to give more structure and consistency to bounds.gms.
Now it contains the following parts:

• Conopt optimisation bounds
• Assumptions onhistorical and near-term capacities
• Assumptions on biomass
• Assumptions on carbon capture and sequestration
• Assumptions and historic values for nuclear energy
• Assumptions for early retirement and phase-out of technologies
• Assumptions for sectors and final energy
• Other bounds

Type of change

Indicate the items relevant for your PR by replacing ◻️ with ☑️.
Do not delete any lines. This makes it easier to understand which areas are affected by your changes and which are not.

Parts concerned

• ☑️ GAMS Code
• ◻️ R-scripts
• ☑️ Documentation (GAMS incode documentation, comments, tutorials)
• ◻️ Input data / CES parameters
• ◻️ Tests, CI/CD (continuous integration/deployment)
• ◻️ Other (please give a description)

Impact

• ◻️ Bug fix
• ☑️ Refactoring
• ◻️ New feature
• ◻️ Change of parameter values or input data (including CES parameters)
• ◻️ Minor change (default scenarios show only small differences)
• ◻️ Fundamental change of results of default scenarios

Checklist

Do not delete any line. Leave unfinished elements unchecked so others know how far along you are.
In the end all checkboxes must be ticked before you can merge.

• I executed the automated model tests (make test) after my final commit and all tests pass (FAIL 0)
• I adjusted the reporting in remind2 if and where it was needed
• My code follows the coding etiquette
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• I updated the CHANGELOG.md correctly (added, changed, fixed, removed, input data/calibration)

Further information (optional)

• Runs with these changes are here: /p/tmp/fabricel/bounds-refactor/202508-refactor-remind
• Comparison of results (what changes by this PR?): very small changes due to a correction of factor 3.66 to 3.6
  /p/tmp/fabricel/bounds-refactor/202508-refactor-remind/compScen-boundsSSP2-2025-08-15_14.09.37-H12.pdf

[LaviniaBaumstark]

Why is this still a draft? Should it be merged for v3.5.1?

[lecfab]

Never had time to properly test and merge it, so it should stay as a draft =(

[fschreyer]

Nice! Thanks for that. I think that improves the structure quite a bit.

Did you test whether the results change? When reordering bounds, it can sometimes happen that one bound now overwrites another which was not intended before?

[fschreyer]

Why is this added?

[lecfab]

i added this set to replace long conditions in the bounds like
loop(te $ (sameas(te, biopyrchp) or sameas(te, biopyrliq) or sameas(te .....

[lecfab]

Thanks for looking through it, I integrated your suggestions and increased the similarity with declarations.gms.

Did you test whether the results change? When reordering bounds, it can sometimes happen that one bound now overwrites another which was not intended before?

Good point: i checked that the bounds are not changed by the re-ordering.
Minor changes happen in the scenarios due to changing a wrong factor 3.66 in to 3.6 (using sm_EJ_2_TWa instead of hard-coded 3.66 * 1e3 / 8760).

[fschreyer]

Looks good. Thanks!

[fschreyer]

Thanks for fixing this! :)