feat(signals): show direct-PR vs issue-discovery tradeoff summary

[JSONbored]

Parent phase: #236
Parent roadmap: #127

Problem

Repo owners and miners need to understand whether a repo is better suited for direct PR work, issue discovery, or neither, without turning that into a public score predictor.

Acceptance criteria

• Summary separates direct-PR fit, issue-discovery fit, maintainer burden, queue pressure, and policy confidence.
• Private scoreability context remains private and authenticated.
• Public-facing wording avoids reward and score-prediction claims.

Validation expected

• Unit tests cover summary classification from deterministic signals.
• Sanitizer tests cover public-safe wording.

Public-output safety criteria

• Public text is sanitized before reaching GitHub comments, issue bodies, PR bodies, extension-visible public panels, or copied public snippets.
• Tests cover forbidden wallet/hotkey, reward-estimate, trust-score, public-score-prediction, private-reviewability, private-scoreability, and farming-language leakage.

Cross-cutting acceptance criteria

• Preserve the repo quality gate: npm run test:ci, 97%+ global coverage, and the local branch coverage target for touched code.
• Keep public/private boundaries explicit. Public GitHub output must not expose wallets, hotkeys, reward estimates, raw trust scores, public score predictions, private reviewability, private scoreability context, or farming language.
• Add/update focused tests for the changed behavior instead of relying on green checks alone.