num_units column in assets.csv

[tsmbland]

Description

This is the first step on the way to making all assets divisible (#1441). This PR makes all assets provided in assets.csv divisible (changing capacity from Continuous to Discrete). Since not all processes have a defined unit_size (and we want to keep this optional), we need an extra column (num_units) specifying how many units to split the capacity into. For processes with a defined unit_size, num_units takes precedence. If n_units is not specified, the behaviour is essentially equivalent to how it currently is: split processes with unit_size according to this, and processes without n_units remain non-divisible (i.e. discrete capacity with a single unit).

This does affect the output files, but only because it changes the num_units column in asset_capacities.csv. Total capacities, flows and prices should be unchanged.

Eventually I want to drop AssetCapacity::Continuous entirely, but it's currently also used by assets invested in by MUSE. This is the next thing to change (#1483)

This PR doesn't make much sense to merge without #1483, but I still figured I'd keep it separate to make it slightly easier to review (#1483 is pretty big so anything to break it up).

Fixes # (issue)

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc
• Update release notes for the latest release if this PR adds a new feature or fixes a bug
  present in the previous release

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[Copilot]

Pull request overview

This PR introduces an explicit num_units field for user-provided assets to support making all assets.csv assets representable as discrete “units”, as an incremental step toward making all assets divisible (Issue #1441). It also standardises naming by renaming AssetCapacity::n_units() to AssetCapacity::num_units() and updates call sites accordingly.

Changes:

• Add optional num_units parsing from assets.csv and derive discrete AssetCapacity from either explicit num_units, process unit_size, or default to a single unit.
• Rename AssetCapacity::n_units() → AssetCapacity::num_units() and update usages in optimisation/output/asset logic.
• Update the input schema (schemas/input/assets.yaml) to document the new num_units column.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/simulation/optimisation.rs	Updates capacity constraint logic to use AssetCapacity::num_units().
src/output.rs	Outputs num_units via the renamed AssetCapacity::num_units() accessor.
src/input/asset.rs	Adds num_units CSV field and constructs discrete AssetCapacity for user assets based on num_units/unit_size.
src/asset/pool.rs	Updates tests/construction to pass explicit AssetCapacity for UserAsset::new.
src/asset/capacity.rs	Renames n_units() to num_units() and updates related tests.
src/asset.rs	Changes UserAsset::new to accept an explicit AssetCapacity and updates internal/tests accordingly.
schemas/input/assets.yaml	Documents the new optional num_units column for assets.csv.

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[codecov]

Codecov Report

❌ Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.91%. Comparing base (f3af853) to head (6cef7f2).
⚠️ Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
src/simulation/optimisation.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1480   +/-   ##
=======================================
  Coverage   89.91%   89.91%           
=======================================
  Files          60       60           
  Lines        8556     8560    +4     
  Branches     8556     8560    +4     
=======================================
+ Hits         7693     7697    +4     
  Misses        543      543           
  Partials      320      320           

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