Feature/aggregation final

[FBumann]

Summary

Major release preparation for v6.0.0 with complete clustering/aggregation rework.

New Features

• Clustering/Aggregation Rework - Complete rewrite of the clustering system with tsam integration, inter-cluster linking, and storage modes (Feature: Clustering IO, single selection, and weights API improvements #549, Clustering Parameter Refinements & Unified Slot Assignment #552)
• fxplot Plotting Accessor - New dataset plotting accessor for enhanced visualization (Feature: fxplot Plotting Accessor #548)
• Comparison Module - Compare results across different FlowSystem solutions (Feature/comparison #550)
• Clustering IO - Save/load clustered FlowSystems with full state preservation (Feature: Clustering IO, single selection, and weights API improvements #549)

Improvements

• Multi-period and multi-scenario clustering support
• Storage model clustering modes (initial=equal, cyclic, decoupled)
• Improved cluster weights and statistics calculations
• New tutorial notebooks for clustering workflows
• CI speedup for notebook execution (ci: Speedup Notebook execution #551)
• Better data for tutorial notebooks (Feature/aggregate rework v2+better data notebooks #542)

Breaking Changes

See CHANGELOG.md for full list of breaking changes in v6.0.0.

Test Plan

• All existing tests pass
• New clustering tests pass
• Notebooks execute without errors
• Documentation builds successfully

Summary by CodeRabbit

• New Features

  • Time‑series clustering (typical periods, peak forcing, storage modes, two‑stage sizing and expand-to-full-resolution), multi‑system Comparison tools, and an xarray .fxplot/.fxstats plotting accessor.

• Documentation

  • Many new/rewritten tutorial notebooks and user‑guide pages with data‑driven examples, realistic profiles, clustering guides, and plotting recipes.

• Chores

  • Docs CI: notebook caching, parallel execution, and execution toggle to speed builds; updated pre-commit excludes for notebook data.

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