Expose configurable routing scorer parameters

[pwltr]

Summary

Adds configurable pathfinding scorer parameters so apps can tune routing behavior instead of always using LDK defaults.

It introduces two new config surfaces:

• ScoringFeeParameters (maps to ProbabilisticScoringFeeParameters)
• ScoringDecayParameters (maps to ProbabilisticScoringDecayParameters)

These can now be set through:

• Config (scoring_fee_params, scoring_decay_params)
• Builder APIs:
  • set_scoring_fee_params(...)
  • set_scoring_decay_params(...)

At build time, ldk-node now uses configured scorer params when constructing a new ProbabilisticScorer (when no persisted scorer exists) and router fee params, falling back to LDK defaults when unset.

Changes and PR description created with agentic assistance

[ldk-reviews-bot]

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