feat(registry): track repo hyperparameter drift severity

[JSONbored]

Parent roadmap: #82

Background

Repo hyperparameters control lane fit and contribution incentives. A small label change and an allocation change should not be treated as the same severity.

Goal

Classify registry hyperparameter drift by affected field and product impact.

Current Behavior

Registry drift reports can show changes, but severity and downstream recommendation impact are not rich enough for operator triage.

Desired Behavior

Maintainers can see whether a registry change affects lane fit, scoreability assumptions, maintainer economics, issue-discovery behavior, or label policy.

Implementation Requirements

• Compare allocation, issue share, maintainer cut, label multipliers, default multiplier, trusted-label flag, fixed base score, and eligibility mode.
• Assign severity and affected surfaces.
• Feed high-impact drift into readiness/admin warnings.
• Keep deterministic sorting of drift events.

Public/Private Output Boundaries

Registry drift is internal/admin-facing by default. Public comments must not claim payout changes or expose score estimates.

Acceptance Criteria

• Field-specific severity is deterministic.
• Label-only drift differs from allocation drift.
• Maintainer cut drift is surfaced to repo owners.
• Drift reports remain bounded for large registry changes.

Testing Requirements

• npm run test:ci must pass.
• Global coverage must remain at or above 97% for lines, statements, functions, and branches.
• Aim for 98%+ branch coverage locally to avoid CI variance.
• Add tests for every new branch, fallback path, sanitizer rule, and regression.
• Add invariant/property-style tests when behavior depends on sorting, gating, scoring, queue pressure, source-upload safety, public/private boundaries, or upstream drift.
• Public GitHub output must be tested against forbidden language: wallet, hotkey, raw trust score, payout, reward estimate, farming, private reviewability, and public score estimate.
• MCP/local tooling must prove source contents are not uploaded.

Additional Test Scenarios

• Each hyperparameter field fixture.
• Multi-field severity ordering.
• Deterministic sorting regression.
• Large registry performance fixture.