feat: configurable timestep selection for the run pipeline (#663)

[joda9]

Add a select_timesteps pipeline task that reduces the analysed time index to a selected subset, in two modes:

• manual: an explicit set/range of timesteps (positioned before the imports so egon_data downloads are restricted to the selected steps);
• auto: the most critical time intervals, via either a power flow (get_most_critical_time_intervals(by="power_flow")) or the residual load (by="residual_load", no power flow — intervals centered on the highest/lowest residual-load steps, snapped to time_step_day_start).

Auto selection may yield two disconnected intervals. pm_optimize now detects a non-contiguous time index and runs a separate, independent OPF per contiguous interval (storage/heat state does not carry across the gap), merging the per-interval results and reporting per-interval solve status. reinforce handles the reduced index unchanged.

Architecture: pipeline tasks stay thin (mode selection + data transfer); the computation lives in edisgo core:

• selection logic in tools.temporal_complexity_reduction (get_most_critical_time_steps/_intervals gain a by mode; public select_two_intervals/intervals_overlap);
• the multi-interval OPF split/merge in opf.powermodels_opf.pm_optimize.

Also:

• EV flexibility bands built in a dedicated build_flexibility_bands task and aligned (year + frequency) to the analysis index in reduce_timeseries_data_to_given_timeindex;
• OPFResults.interval_results for the per-interval solve report;
• config surface: a top-level timeseries_selection block + uc5_select_timesteps preset + run_example_05.py;
• tests in tests/run, tests/tools, tests/opf.

Description

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Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• New and adjusted code is formatted using the pre-commit hooks
• New and adjusted code includes type hinting now
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
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• If new packages are needed, I added them the setup.py, and if needed the rtd_requirements.txt, the eDisGo_env.yml and the eDisGo_env_dev.yml.
• I have added new features to the corresponding whatsnew file