feat(cpp): add code coverage

[slbotbm]

Which issue does this PR address?

None

Rationale

cpp sdk did not have code coverage, so this pr adds it.

What changed?

TODO

Local Execution

• passed
• Pre-commit hooks ran

AI Usage

If AI tools were used, please answer:

1. Which tools? codex
2. Scope of usage? code generation
3. How did you verify the generated code works correctly? tested it multiple times
4. Can you explain every line of the code if asked? TODO

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.36%. Comparing base (dc2b382) to head (deadede).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #4118      +/-   ##
============================================
- Coverage     86.38%   86.36%   -0.03%     
  Complexity     1455     1455              
============================================
  Files          1259     1267       +8     
  Lines        205992   208308    +2316     
  Branches     171193   171331     +138     
============================================
+ Hits         177955   179900    +1945     
- Misses        23597    23829     +232     
- Partials       4440     4579     +139     

Components	Coverage Δ
Rust Core	87.32% <ø> (-0.01%)	⬇️
Java SDK	67.58% <ø> (ø)
C# SDK	76.97% <ø> (ø)
Python SDK	91.34% <ø> (ø)
PHP SDK	85.65% <ø> (ø)
Node SDK	96.26% <ø> (+0.08%)	⬆️
Go SDK	69.43% <ø> (+0.03%)	⬆️
C++ SDK	83.98% <83.33%> (∅)
see 43 files with indirect coverage changes

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