[DOC-02] Add documentation of the `optim-config.yml` file

[tbittar]

Type of Change

New content

Description

The optim-config.yml is currently not documented in the GEMS repo. Only a (hidden) remark in the investment example page refers to this file and link to the gemspy repo (besides this file is not used in the investment example). Therefore some of the GEMS feature are not exposed in the documentation.

Affected Documentation Sections

Create a new page doc/user-guide/file-structure/optimization-configuration.md. Also in mkdocs.yml, rename Solver parameters and optimization configuration files to Solver parameters not to mix parameters and optimisation configuration.

Process Checklist

Step 1 — Issue Creation

• Issue created and linked to process DOC-02

Step 2 — Triage

• Process confirmed applicable
• Assigned to responsible contributor
• Priority and milestone set (if applicable)

Step 3 — Impact Analysis

• Affected documentation sections identified
• Inconsistencies between documentation and existing implementation identified
• Assessed whether change affects the GEMS Language definition (or is purely editorial/structural)
• No undocumented behavior will be introduced

Step 4 — Implementation

• Documentation pages updated
• Internal links verified
• No inconsistency introduced between documentation and implementation

Step 5 — Testing & Validation

• All documentation examples validated (no broken or incorrect examples)

Step 6 — CI Validation

• Documentation build passes (mkdocs build) without warnings

Step 7 — Review & Merge

• PR reviewed alongside documentation changes

Step 8 — Versioning ⚠️ patch bump only (or none for purely editorial changes)

• If purely editorial/structural: no version bump required; if language clarification: a documentation patch release is expected

Step 9 — Supporting Files

• If language clarification: release notes entry added (doc/0_Home/4_release_notes.md)
• AGENTS.md reviewed for impact and updated if needed

Step 10 — Release

• If a release is needed: follow the release process in the Developer Guidelines