feat(settings): add repo policy compiler for focus manifests

[JSONbored]

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

Goal

Compile repo focus manifests into concrete owner and maintainer guidance: contribution lanes, label policy, onboarding pack inputs, readiness warnings, and Gittensor-specific tradeoffs.

This issue is now a mini-epic. Do not implement the whole policy compiler in one PR; use the focused child issues below.

Child issues

• feat(settings): define focus-manifest policy schema #296 define focus-manifest policy schema
• feat(settings): derive contribution lanes from focus manifests #297 derive contribution lanes from focus manifests
• feat(settings): emit repo readiness warnings from policy compiler #298 emit repo readiness warnings from policy compiler
• feat(settings): feed policy compiler output into onboarding packs #299 feed policy compiler output into onboarding packs
• test(settings): add policy compiler sanitizer fixtures #300 add policy compiler sanitizer fixtures

Done when

• The policy schema, contribution lanes, readiness warnings, onboarding-pack handoff, and sanitizer fixtures are complete or intentionally superseded.
• feat(settings): generate repo onboarding pack for accepted Gittensory repos #248 can consume compiler output without replacing feat(settings): generate repo onboarding pack for accepted Gittensory repos #248.
• Repo owners can preview warnings before inviting more contributor traffic.

Non-goals

• No public reward prediction or public scoring.
• No wallet, hotkey, raw trust, private scoreability, or private reviewability output.
• No autonomous issue filing, PR creation, comments, labels, closure, or merge behavior.

Validation expected

• Child PRs should include focus manifest fixtures, schema/normalization tests, sanitizer coverage, and npm run test:ci.