docs(launch): create miner quickstart by contribution lane

[JSONbored]

Parent phase: #238
Parent roadmap: #127

Problem

Miner onboarding should be organized by how someone contributes: direct PR, issue-solving PR, issue discovery, docs/context work, and repo-specific lanes. Generic setup docs are not enough for broad ecosystem adoption.

Acceptance criteria

• Quickstart explains lane choice, install, auth, doctor, plan, preflight, PR packet generation, and validation expectations.
• Docs avoid reward guarantees and public score-prediction language.
• CLI commands match the current MCP package behavior.

Validation expected

• Docs link to current commands and pass docs lint/build if applicable.
• MCP command examples include JSON-output and redaction notes where relevant.

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.

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.