feat(settings): feed policy compiler output into onboarding packs

[JSONbored]

Parent roadmap: #127
Parent phase: #236
Parent epic: #277
Related advanced phase: #269
Related onboarding issue: #248

Goal

Connect policy compiler output to accepted-repo onboarding pack inputs without replacing #248.

Requirements

• Provide the data handoff feat(settings): generate repo onboarding pack for accepted Gittensory repos #248 needs for contribution lanes, label policy, validation expectations, and readiness warnings.
• Keep onboarding text generation previewable before publication.
• Do not build the full onboarding pack UI/export in this issue.

Acceptance criteria

• feat(settings): generate repo onboarding pack for accepted Gittensory repos #248 can consume policy compiler output through a stable interface or fixture.

• Generated public text remains sanitized.

• Private owner context is not leaked into public onboarding material.

• This is not autonomous issue filing, PR creation, commenting, labeling, closure, or merge.

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

Validation expected

• Cross-link fixture between policy compiler output and onboarding-pack input.
• Public/private sanitizer tests.
• npm run test:ci.