Converge the `scoring`/`rules` twins

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Problem: The gate-decision advisory logic exists as two hand-maintained "twin" files today — one in src/, one already in gittensory-engine — and they're deliberately allowed to structurally diverge, specifically so the engine's copy doesn't have to pull the entire, much larger signals-engine file into the miner's own dependency graph. Whether to converge these to one real source, or keep them intentionally separate, is a real decision, not a mechanical move.

Area: ORB / gittensory-engine

Proposal: Evaluate each twin pair individually. For any pair where divergence no longer serves a real purpose, converge to one source with a shim. For the one pair explicitly documented as deliberately divergent, either keep it that way (documenting why, clearly, for future contributors) or design a way to satisfy both constraints (e.g. a shared type-only import that doesn't pull the larger file's implementation along with it).

Deliverables:

• A clear, documented decision — converge or keep-divergent — for every twin pair in this area, not a blanket policy.

Acceptance criteria:

• No gate-decision behavior changes as a result of this issue — this is the one phase where "no behavior change" needs to be actively verified, not just assumed from a clean diff.

Boundaries:

• Don't converge the deliberately-divergent pair without first solving the dependency-graph-size problem it exists to avoid.

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JSO-3541