fix: hide empty nested objects with -e flag

[pamburus]

Apply hide_empty_fields recursively to nested object fields and hide objects that become empty after filtering. Use single-pass approach with buffer rollback to avoid double-parsing.

• Hide empty nested fields when flattening (default behavior)
• Hide empty objects and objects with all empty fields
• Show ellipsis (...) indicator when fields are hidden
• Efficient single-pass implementation with buffer rollback

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.12%. Comparing base (8c83331) to head (3e251bb).
⚠️ Report is 78 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1186      +/-   ##
==========================================
+ Coverage   84.10%   84.12%   +0.02%     
==========================================
  Files          47       47              
  Lines        9453     9465      +12     
==========================================
+ Hits         7950     7962      +12     
  Misses       1503     1503              

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