feat: add configurable scoring fee/decay parameters

[pwltr]

Summary

This PR 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/deserializing the ProbabilisticScorer and router fee params, falling back to LDK defaults when unset.

Why this is needed

Probe and payment outcomes are sensitive to scorer behavior (penalty model + decay dynamics). With hardcoded defaults, consumers cannot adapt routing to their environment (e.g., aggressive probing diversity vs conservative reliability). This change makes scorer behavior explicit

[chatgpt-codex-connector]

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[piotr-iohk]

Also cargo fmt --check fails on this branch. Rev: ed6ea2e.

[pwltr]

Also cargo fmt --check fails on this branch. Rev: ed6ea2e.

Addressed both comments 5b9fe28

[piotr-iohk]

utACK

I checked the latest head locally.

Verified:

• cargo fmt --check passes now (only stable rustfmt warnings from unstable config keys).
• cargo test set_scoring_params_updates_builder_config passes.
• Previous Package.swift same-tag/checksum concern is addressed by bumping to v0.7.0-rc.52.
• The old Codex comments look outdated against the current diff.

Two things I’m not 100% sure about before/around merge:

• bindings/python/pyproject.toml still shows 0.7.0-rc.50 while the other version files are 0.7.0-rc.52. Maybe intentional if Python is not being released here.
• Package.swift now points to v0.7.0-rc.52, but I don’t see that GitHub release yet. Before consumers use this tag, we should publish v0.7.0-rc.52 and verify the LDKNodeFFI.xcframework.zip checksum matches Package.swift.