Add a tree view to search UI

[jerbly]

Add a tree view to the serve UI's search page, grouping results by namespace with expand/collapse controls, and a "Hide deprecated" toggle (on by default) for both the list and tree views.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.2%. Comparing base (554e3f1) to head (2d46d80).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1595   +/-   ##
=====================================
  Coverage   81.1%   81.2%           
=====================================
  Files        130     130           
  Lines      11460   11463    +3     
=====================================
+ Hits        9305    9308    +3     
  Misses      2155    2155           

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