feat(mcp): make doctor output a miner onboarding checklist

[JSONbored]

Parent phase: #234
Parent roadmap: #127

Problem

Doctor should be the miner first-run checklist, not just a diagnostics dump. It needs to tell a miner exactly what is configured, what is missing, and the next command to run.

Acceptance criteria

• Doctor groups checks into auth, API compatibility, local repo readiness, scorer availability, output safety, and next command.
• Human output stays concise and action-oriented.
• JSON output is stable enough for app/Raycast/automation consumers.
• Unsupported source upload is explicit and fails closed.

Validation expected

• CLI unit tests cover healthy, unauthenticated, stale API, missing repo, and unsupported upload states.
• Snapshot or schema tests cover JSON output shape.

MCP/CLI acceptance criteria

• Machine-readable JSON output is available where automation needs it.
• Token, wallet/hotkey, and local absolute-path redaction are covered by tests.
• Source-upload behavior remains explicit and fails closed where upload is unsupported.

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.