Remove redundant tracing module tests

[Copilot]

Removed three low-value test functions from the tracing module that provided minimal coverage:

• test_span_exporter_timeout - Only validated a constant value
• test_log_levels - Tested standard library enum comparison behavior
• test_worker_guards_structure - Created empty vector and verified .len() returns 0

The remaining three tests provide meaningful coverage:

• test_init_tracing_comprehensive - Validates tracing initialization, log directory creation, and guard lifecycle
• test_host_struct_can_be_created - Tests Host struct instantiation with proper field values
• test_temp_dir_and_file_creation - Validates filesystem operations for log paths

Net reduction: 33 lines

Warning

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• esm.ubuntu.com
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---

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[gaius-qi]

LGTM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.25%. Comparing base (41f6c0d) to head (b10c84e).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1655      +/-   ##
==========================================
+ Coverage   49.51%   50.25%   +0.73%     
==========================================
  Files          82       82              
  Lines       19698    19809     +111     
==========================================
+ Hits         9754     9955     +201     
+ Misses       9944     9854      -90     

Files with missing lines	Coverage Δ
dragonfly-client/src/tracing/mod.rs	50.20% <100.00%> (+50.20%)	⬆️

... and 4 files with indirect coverage changes

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[chlins]

lgtm