feat(analytics): persist recommendation outcome events

[JSONbored]

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

Goal

Persist private recommendation outcome events as the data spine for later recommendation quality analytics.

Requirements

• Track accepted, rejected, ignored, stale, merged, closed, and improved outcome events where the product already has enough signal.
• Separate role, surface, recommendation id, and snapshot id where available.
• Keep event storage private and avoid public GitHub output.

Acceptance criteria

• Outcome events can be recorded without exposing private context publicly.

• Event shape supports later classification and rollups.

• Public surfaces do not expose private scoreability, reward/risk, wallet, hotkey, raw trust, or private reviewability.

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

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

Validation expected

• Event persistence fixtures for accepted, rejected, ignored, stale, merged, closed, and improved outcomes.
• Privacy/sanitizer tests for event serialization.
• npm run test:ci.