Run3 visualization logic implementation

Implement visualization.js with the following structure:

1. Wrap logic in document.addEventListener('DOMContentLoaded', async () => { ... });.
2. Load data: Use d3.csv("./data/stock-descriptions.csv").
3. Bubble Chart:
   • Define a d3.forceSimulation.
   • Use d3.forceX and d3.forceY grouped by sector name to create clusters.
   • Use d3.forceCollide based on bubble radius to prevent overlap.
   • Scale radius using d3.scaleSqrt for market cap (handle missing values for ETFs).
4. Tooltips: Append a hidden div to the body. On mouseover, update and show the tooltip for stocks (filter out ETFs using the sector or market cap null-check).
5. Interactivity:
   • Add click listeners to circles to add a CSS class (e.g., .highlight) and trigger scrollIntoView on the corresponding table row.
   • Add click listeners to table rows to find the corresponding bubble and highlight it.