Reduction problem size by adding conditions on constraint construction

[willu47]

I've added a few small conditions to constraints following these rough guidelines:

• trade constraints should not be created when r and rr are equal
• all constraints with Produce only need to be generated when there are corresponding non-zero values in the OutputActivityRatio
• all constraints with Use only need to be generated when there are corresponding non-zero values in the InputActivityRatio
• Also fixed an issue with incorrect index in constraint OC1 causing the variable cost to be calculated for every timeslice.

[Copilot]

Pull Request Overview

This PR reduces model size by adding conditional filters to constraint definitions, restricts trade flows to distinct regions, and corrects an indexing issue in the operating cost constraint.

• Added filter expressions to avoid generating constraints when activity ratios are zero
• Restricted Trade variable and related constraints to r <> rr
• Corrected the OC1 constraint by updating its index list

Comments suppressed due to low confidence (1)

src/osemosys.txt:604

• The OC1 constraint removed the l in TIMESLICE index but its body still references the timeslice dimension; reintroduce l in TIMESLICE in the index list or adjust the body to remove l references.

s.t. OC1_OperatingCostsVariable{r in REGION, t in TECHNOLOGY, y in YEAR: sum{m in MODE_OF_OPERATION} VariableCost[r,t,m,y] <> 0}: