feat: persist active sheet in URL

[jimniels]

Per this conversation in Slack, this updates the app so the current active sheet is stored in the URL (and therefore part of the share process).

Functionality:

• When the user changes to any sheet (other than the first one), the URL updates to include a sheet param indicating which sheet is currently active, e.g. ?sheet=Sheet%201
• When the user changes to the first sheet, the sheet param is removed

To test:

• Change the active sheet in the sheet bar (or command palette) and see the active sheet show up in the URL bar.
• Share the link to a sheet and see that it contains the active sheet in the URL

---

This also resolves an older issue by introducing the functionality into the app.

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Name	Status	Preview	Updated (UTC)
quadratic	✅ Ready (Inspect)	Visit Preview	Dec 20, 2024 9:32pm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.82%. Comparing base (a26883a) to head (47ba78b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2139   +/-   ##
=======================================
  Coverage   90.82%   90.82%           
=======================================
  Files         260      260           
  Lines       57583    57583           
=======================================
  Hits        52297    52297           
  Misses       5286     5286           

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