feat(analytics): add role-aware recommendation quality rollups

[JSONbored]

Parent roadmap: #127
Parent phase: #237
Parent epic: #278
Related advanced phase: #269
Related base feedback issue: #96

Goal

Aggregate recommendation quality privately by role and surface so Gittensory can measure whether guidance is useful.

Requirements

• Roll up recommendation quality by role, surface, time window, and outcome category.
• Separate maintainer-lane outcomes from normal contributor-lane outcomes.
• Keep rollups private unless explicitly exposed through a sanitized authenticated surface.

Acceptance criteria

• Role-aware rollups can report quality over time without public scoring claims.
• Maintainer-lane and contributor-lane analytics are not mixed accidentally.
• Public surfaces avoid private scoreability, reward/risk, wallet, hotkey, raw trust, and private reviewability.
• This is not an autonomous PR bot.

Validation expected

• Rollup tests for role, surface, time-window, and lane separation.
• Public/private sanitizer tests.
• npm run test:ci.