chore: remove central node and associated code

[aboydnw]

Another cleanup to remove some unnecessary code. This used to be a visual element for a center node in the middle of the chart that I removed to make it visually cleaner. From here I think we can start playing with things like font size and filtering to make the visual easier to scan.

To test:

1. Make sure chart elements and interactions still function
2. Make sure title still says "Development Seed"

[aboydnw]

I reordered the contributors alphabetically because the symmetry of the chart in the screenshot above was annoying me 😅 so here is an updated screenshot

Also, something we get for free with this change is that when you apply a filter the chart simplifies to only show contributors with links to the filtered repos. We got this for free on this PR because now there is no central node creating a "fake link." I'm okay with this functionality for now, although open to feedback. In future stories I want to work on the filtering functionality so we can improve this interaction then.

[gadomski]

I like it! I don't know if it happened with this PR or previously, but mousing over a indvidual's circle doesn't appear to give them a popup anymore. I'm cool with merging this and fixing that as a follow-on.

Screen.Recording.2026-02-10.at.3.55.19.AM.mov