Update modeledyears handling in parser and file mapping

[mcllerena]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the handling of modeled years data to standardize its naming and improve data structure parsing. The changes address inconsistencies between file mapping configuration and parser logic for accessing modeled years information.

• Updates file mapping from "modeledyears" to "modeled_years" for consistency
• Modifies parser to access modeled years data as a proper column instead of row-based access
• Adds schema and pivot configuration for better data structure handling

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/r2x_reeds/parser.py	Updates variable references and data access pattern for modeled years
src/r2x_reeds/config/file_mapping.json	Renames mapping from "modeledyears" to "modeled_years" and adds schema configuration

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[mcllerena]

It is failing 'cause it's depending on ml/create-pivot-func branch in r2x-core (already in PR)