feat: added pixi env and R circos plot example

[m-jahn]

No description provided.

[Copilot]

Pull request overview

Adds an R-based Circos plotting example to the repo and introduces a pixi environment to make running the notebook reproducible.

Changes:

• Added source/circlize.R with helper functions to validate genomic coordinates, compute GC metrics, and generate a circlize genome plot.
• Added pipeline/plot_circos.Rmd tutorial notebook and linked it from the README.
• Added pixi.toml/pixi.lock plus git config updates to support a circlize pixi environment.

Reviewed changes

Copilot reviewed 5 out of 8 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
source/circlize.R	New plotting utilities (validation, GC metrics, circlize tracks).
pipeline/plot_circos.Rmd	New R notebook demonstrating how to generate the plot using the utilities.
README.md	Adds link to the new rendered circlize notebook.
pixi.toml	Defines a circlize feature/environment and a render task for the notebook.
pixi.lock	Locks the pixi environment for reproducible installs.
.gitignore	Ignores local .pixi/ environment files (except config).
.gitattributes	Marks pixi.lock as generated/binary merge behavior and adjusts linguist settings.

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