Unnecessary capacity investment

## Describe the bug

In the attached model, in the 2nd MSY (2021) investment occurs in OILREF and OILRF2. However, as far as I can tell, the additional capacity is not needed. The additional investment corresponds to 1 tranche of capacity for each.

The issue appears to be related to how the activity of the tranches of assets is netted off the total demand profile for each downstream commodity. Somehow, the combined activity of the 3 - 4 tranches of capacity in each asset is less than the potential activity (in final dispatch) of the 3 - 4 tranches combined. As the output commodity is seasonally balanced here, perhaps there's some arbitrariness to where the output falls, leading to some apparent remaining demand after all tranches have been retained in the investment appraisal process? There could be other explanations, but if this is correct, is there a way we can make sure time sliced output is flat in the case of seasonally / annually balanced commodities?

## To Reproduce

Run the attached model (on main development branch, as at 09/09/2026)

## Expected behavior

No additional capacity investment should occur in these processes.

[simple_modified_nostor.zip](https://github.com/user-attachments/files/32006227/simple_modified_nostor.zip)