chore: increase coverage threshold from 85% to 90%

[mvillmow]

Summary

Increase the code coverage threshold from 85% to 90% as per issue #341.

This is the first step in the incremental approach to raise coverage thresholds:

• 85% → 90% (this PR)
• 90% → 95% (future PR)

Test plan

• Verify pyproject.toml coverage fail_under threshold updated
• CI/coverage checks will enforce new threshold

[github-actions]

✅ Dependency Audit

Severity	Count
Critical	0
High	0
Medium	0
Low	0

See the Security tab for detailed findings.

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Workflow: Dependency Audit

[github-actions]

Security Scan Results

• ❌ Secret Scanning: Potential secrets found
• ✅ SAST: Completed (check Security tab for details)
• ✅ Dependency Scanning: Completed
• ✅ C++ Static Analysis: Completed
• ✅ Docker Image Scanning: 0 high, 22 medium vulnerabilities (acceptable)

Recommendations

• Review findings in the GitHub Security tab
• Check artifact uploads for detailed reports
• Address critical Docker vulnerabilities immediately

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Workflow: Security Scanning