Viz 01: Unify cluster palette and add discrete palette

[Doresic]

The cluster-coloured plotters (waterfall, parameters, optimization_stats, optimizer_history, profiles) all had their cluster palette hardcoded with no user override path. That default sometimes produced indistinguishable cluster colours. As @PaulJonasJost suggested, a default categorical palette works better. One can change it using a style_kwargs override path. I also added a guarantee the palette stays far from the MLE (default red) and isolated point (default grey) colors.

Main changes:

• new pypesto/visualize/_style.py with the reserved colours (MLE_COLOR = tab:red for the best cluster, OUTLIER_COLOR for singletons) and the cycled palette source (CMAP_DISCRETE, default "tab10"), plus a small resolve_style helper
• _build_cluster_palette samples non-best cluster colours from cmap_discrete with a small distance filter — that way the reserved best/outlier colours stay visually distinct from the cycled ones even when someone passes a cmap that happens to contain red or grey
• style: dict | None threaded through assign_clustered_colors, assign_colors, assign_colors_for_list, process_result_list
• the 5 top-level plotters get a new style_kwargs: dict | None = None kwarg; their lowlevel counterparts (waterfall_lowlevel, parameters_lowlevel, optimizer_history_lowlevel, stats_lowlevel) take an already-resolved style: dict | None = None. So resolve_style runs exactly once per call chain at the user-facing boundary.

This is the first in a small series of visualisation PRs. The rest of _style.py (constants for bounds, scatter, colorbars, …) grows incrementally as later PRs polish each visualisation family.

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Codecov Report

❌ Patch coverage is 90.32258% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.33%. Comparing base (7255fc7) to head (450b571).

Files with missing lines	Patch %	Lines
pypesto/visualize/_style.py	71.42%	4 Missing ⚠️
pypesto/visualize/clust_color.py	92.30%	2 Missing ⚠️
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Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1716      +/-   ##
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- Coverage    84.35%   84.33%   -0.03%     
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  Files          164      165       +1     
  Lines        14752    14796      +44     
===========================================
+ Hits         12444    12478      +34     
- Misses        2308     2318      +10     

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[Copilot]

Pull request overview

This PR introduces a unified, user-overridable visualization style mechanism for cluster-related coloring across multiple pypesto.visualize plotters, switching defaults to a categorical palette and reserving distinct colors for the MLE and singleton/outlier starts.

Changes:

• Added pypesto.visualize._style with default style constants and a resolve_style(style_kwargs) helper.
• Threaded a resolved style dict through color assignment utilities and result-list processing to ensure consistent palette selection.
• Added style_kwargs to user-facing plotters and style to low-level plotting functions to avoid repeated style resolution.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pypesto/visualize/_style.py	New style registry/constants and resolve_style merge+warning helper.
pypesto/visualize/clust_color.py	Uses a discrete/categorical palette with filtering to keep MLE/outlier colors distinct; propagates style.
pypesto/visualize/misc.py	Threads style into process_result_list so per-result palettes use the resolved style.
pypesto/visualize/waterfall.py	Adds style_kwargs and forwards resolved style into coloring/lowlevel routines.
pypesto/visualize/parameters.py	Adds style_kwargs and forwards resolved style into coloring/lowlevel routines.
pypesto/visualize/optimizer_history.py	Adds style_kwargs and forwards resolved style into coloring/lowlevel routines.
pypesto/visualize/optimization_stats.py	Adds style_kwargs and forwards resolved style into coloring/palette selection and lowlevel routines.
pypesto/visualize/profiles.py	Adds style_kwargs and forwards resolved style through result/profile-list processing.

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