BUG: Preserve complete component tidal parameters

[nomad3]

Summary

This pull request prevents repeated binary-neutron-star parameter conversion from overwriting a complete pair of explicitly supplied component tidal deformabilities.

When both lambda_1 and lambda_2 are present and non-None, the converter now preserves them instead of reconstructing them from lambda_tilde or delta_lambda_tilde. Derived-only, partial-component, and None inputs continue through the existing reconstruction paths.

The regression uses the reported component values and covers both mixed forms: lambda_tilde alone and lambda_tilde with delta_lambda_tilde. Before the fix, these changed lambda_1=0.0 to approximately 0.3695 and -2.46e-14, respectively.

This does not add numerical clamping, consistency validation, or waveform changes.

Fixes #1114

Testing

• pytest -q test/gw/conversion_test.py — 65 passed, 2 subtests passed
• Existing derived-only and partial-component conversion controls
• Bilby-pinned flake8 and codespell checks
• git diff --check

This is a draft pending final author review and maintainer confirmation of the narrowly scoped precedence behavior.