Constrain zarr dependency to <3.0

[bendichter]

Summary

• Pin zarr to >=2.16.1,<3 to prevent installation of zarr 3.x, which has breaking API changes

Test plan

• Existing tests continue to pass with zarr 2.x

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.39%. Comparing base (d2296a4) to head (c18dfd1).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #122      +/-   ##
==========================================
- Coverage   81.43%   81.39%   -0.05%     
==========================================
  Files          30       30              
  Lines        2790     2784       -6     
==========================================
- Hits         2272     2266       -6     
  Misses        518      518              

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