feat(settings): derive contribution lanes from focus manifests

[JSONbored]

Parent roadmap: #127
Parent phase: #236
Parent epic: #277
Related advanced phase: #269

Goal

Compile focus manifest inputs into clear contribution lanes contributors and repo owners can use.

Requirements

• Derive preferred lanes, discouraged lanes, validation expectations, and issue/PR entry guidance.
• Keep results deterministic and explainable.
• Avoid onboarding-pack generation or readiness-warning expansion in this issue.

Acceptance criteria

• Contribution lanes are generated from representative focus manifest fixtures.

• Lane output is public-safe and previewable before publication.

• Output does not expose private scoreability, reviewability, reward/risk, wallet, hotkey, or raw trust context.

• This is not autonomous issue filing or PR creation.

• This is not an autonomous PR bot and not public scoring.

Validation expected

• Lane derivation fixture tests.
• Public sanitizer tests for generated guidance.
• npm run test:ci.