Add tabulator filter placeholder

[ahuang11]

The text input was confusing to me without context, so I added a placeholder

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 61.18%. Comparing base (049a997) to head (0b571ee).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lumen/ai/agents.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #741      +/-   ##
==========================================
- Coverage   61.22%   61.18%   -0.04%     
==========================================
  Files         101      101              
  Lines       12352    12371      +19     
==========================================
+ Hits         7562     7569       +7     
- Misses       4790     4802      +12     

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