fix: DH-17730: Fix Proxy Model Undefined Formatter

[dgodinez-dh]

Fixes https://deephaven.atlassian.net/browse/DH-17730 in Enterprise. Will need to be cherry picked back to v0.85.
web-client-ui issue is #2234

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.42%. Comparing base (a24dc8c) to head (65ef9d9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2237      +/-   ##
==========================================
- Coverage   46.64%   46.42%   -0.22%     
==========================================
  Files         694      698       +4     
  Lines       38517    38751     +234     
  Branches     9742     9677      -65     
==========================================
+ Hits        17965    17991      +26     
- Misses      20499    20749     +250     
+ Partials       53       11      -42     

Flag	Coverage Δ
unit	46.42% <100.00%> (-0.22%)	⬇️

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