chore: improve kube maintenance path

[oab24413gmai]

Summary:

• Add additional unit tests in kube-core/src/params.rs covering edge cases of the query-string serialization for ListParams/WatchParams/PatchParams builders — e.g. behavior when label_selector/field_selector are empty strings, combining timeout + bookmarks, and verifying that resource_version='0' is preserved rather than dropped. Pure additive tests against existing public APIs, no behavioral change.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.8%. Comparing base (1f5a46b) to head (228759b).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1988     +/-   ##
=======================================
+ Coverage   76.7%   76.8%   +0.1%     
=======================================
  Files         89      89             
  Lines       8747    8792     +45     
=======================================
+ Hits        6703    6745     +42     
- Misses      2044    2047      +3     

Files with missing lines	Coverage Δ
kube-core/src/params.rs	87.9% <100.0%> (+2.5%)	⬆️

... and 6 files with indirect coverage changes

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[clux]

Thanks for this, nicely scoped. Clear.

[clux]

Are you able to run just fmt and commit with --signoff?