feat: unversioned proceedings cache

[jennifer-richards]

Avoids invalidating the cache on every new release. Future work: provide a convenient way to re-compute quckly if an important change needs to get picked up.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.90%. Comparing base (8fbbc55) to head (c730a73).
⚠️ Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9779      +/-   ##
==========================================
+ Coverage   88.87%   88.90%   +0.02%     
==========================================
  Files         319      316       -3     
  Lines       41925    41992      +67     
==========================================
+ Hits        37260    37331      +71     
+ Misses       4665     4661       -4     

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