Refactor: initiative pills change hash

[thekaveman]

Quick follow-up to #363

• Update the URL so it matches the initiative the user is looking at
• Logic that shows a pill's content is now tied to the hash being changed
• Inserts initiative content into user's history

How to test

1. Run the app locally
2. Ensure the existing behavior of going directly to e.g. http://localhost:4000/#initiatives-gtfs still loads that pill content
3. Change pills
4. Observe the window.location.hash value update accordingly
5. Observe the associated pill content become visible
6. Click the back button
7. Observe the previous hash / pill content is visible

Demos

Loading the page with a hash link

https://github.com/user-attachments/assets/382b3130-f173-459f-93b0-f68bbaab0a3d

Clicking pills and the back button

https://github.com/user-attachments/assets/19298fa6-a8c1-4123-a27e-9196a80c1c83

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