Graph Visualization

# Bounty Points: 350

## Branch Instructions
push changes to a new *'visualize'* branch

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**Explanation:**

* No **visual representation** of traffic network
* Cannot see car distribution or path taken
* Difficult to **debug** or understand simulation behavior

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### Possible fix/approach:

* Use **`NetworkX`** + **`Matplotlib`** for graph visualization
* Display nodes with **car counts** (size or color-coded)
* Show edges with weights
* Highlight **subject car's path**
* Optional: **animate** state changes over time
* Save output as image file

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### Features to include:

* **Node labels** (A, B, C, etc.)
* **Edge weights** (travel times)
* **Car count** at each node
* **Current path highlighting**
* **Legend** explaining visualization

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### Maintainer notes:

* Should generate visualization at **end of simulation**
* Optional flag to **enable/disable** (don't force dependency)
* Keep it simple - **static image** is acceptable

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### Resources:

* NetworkX visualization: `https://networkx.org/documentation/stable/reference/drawing.html`
* Matplotlib documentation

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