Fix shape_example: migrate from ModularServer to SolaraViz (Mesa 3.x)

[Harshini2411]

Partially addresses #358

Changes

shape_example:

• Deleted server.py (old ModularServer approach)
• Created app.py using SolaraViz + make_space_component
• Updated Walker to extend CellAgent, added step() method
• Updated run.py
• Note: arrowHead not supported in Mesa 3.x, replaced with marker="^"

charts:

• Deleted server.py (old ModularServer approach)
• Created app.py using SolaraViz, make_space_component, make_plot_component
• Uses AgentPortrayalStyle to fix FutureWarning
• Uses solara.Reactive to fix render loop
• Updated run.py

Fixes #358

[Harshini2411]

@quaquel ready for review! This PR fixes both shape_example and charts,
fully addressing #358. Could you approve the CI workflow? Thank you!

[EwoutH]

Cool, these visualisation updates are appreciated!

Could you:

• Checkout the test failure
• Add a screenshot or gif of the visualisation to the PR description
• Request a peer-review (and maybe do one or two yourself)

[Harshini2411]

Hi @EwoutH! Thanks for the feedback!

• CI failure fixed ,the issue was a UTF-16 encoded .gitignore file, converted to UTF-8
• Added screenshots of both shape_example and charts visualizations to the PR description
• Shape_Example

• Charts

Please let me know if anything else needs to be addressed!

[Harshini2411]

@EwoutH Also fixed and tested hex_ant and hex_snowflake locally:

• hex_ant: restructured into package with nested folder, fixed PropertyLayer .data assignments

• hex_snowflake: restructured into package with nested folder, fixed imports