Update prices in the base year

[tsmbland]

Prices were previously not being updated in the base year, sticking to the values provided in the projections file (or zero if not provided), whereas all subsequent years return endogenously calculated prices (if available).

However, there's no particularly good reason why we can't return endogenous prices for the base year, so in the interests of consistency I've changed this.

I've also tried to clarify the documentation to make it clearer how the projections file is used and the consequences for omitting certain price projections.

You can see the implications of this in the results files for the example models. Apart from changing prices in the first year, this doesn't have any impact, because prices are (with certain exceptions) only used to make investment decisions, and there are no investments in the base year. Still nice to see these numbers, and this will also prevent potentially sharp price changes from the first year to the second year.

With this change there's really no need to provide price projections for commodities that can be produced in the model, except that if they don't have a projection they'll end up with a price of zero until the first time they're actually produced.

[Copilot]

Pull request overview

This PR updates the MCA equilibrium loop so that endogenously calculated prices are also applied in the base year (when running in equilibrium mode), instead of leaving base-year prices at the projections/zero defaults, and refreshes the regression “golden” outputs accordingly. It also clarifies projections-file behavior in the docs and fixes a working-directory handling issue in the example-output runner.

Changes:

• Update equilibrium price-updating logic so base-year prices can be endogenously updated (first iteration) and carried into stored results.
• Update documentation describing how/when projections are used (and what happens when they’re omitted).
• Refresh example/tutorial regression outputs and fix run_models.py to run in stable per-example directories and restore CWD.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/muse/mca.py	Updates equilibrium/run logic so base-year prices are updated (first iteration) and price updates apply to the intended year set.
docs/inputs/projections.rst	Clarifies when price projections are optional/required and how missing projections are interpreted.
tests/example_outputs/run_models.py	Runs examples in directories relative to the script and restores the previous working directory.
tests/example_outputs/trade/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/multiple_agents/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/minimum_service/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/medium/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/default_timeslice/Results/Power_Supply.csv	Reorders/updates expected output rows due to regenerated results.
tests/example_outputs/default_timeslice/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/default_retro/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/default_correlation/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/default_adhoc/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
tests/example_outputs/default/Results/MCAPrices.csv	Updates expected base-year prices in regression output.
docs/tutorial-code/new-decision-metric/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/modify-timing-data/2-modify-time-framework/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/modify-timing-data/1-modify-timeslices/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/min-max-timeslice-constraints/2-max-constraint/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/min-max-timeslice-constraints/1-min-constraint/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/carbon-budget/1-carbon-budget/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-service-demand/1-exogenous-demand/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-service-demand-subsectors/2-agents/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-service-demand-subsectors/1-residential-subsectors/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-region/1-new-region/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-new-technology/2-scenario/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-new-technology/1-introduction/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-correlation-demand/1-correlation/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-agent/2-multiple-objective/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.
docs/tutorial-code/add-agent/1-single-objective/Results/MCAPrices.csv	Updates expected base-year prices in tutorial output.

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