Add challenge deadline fairness guard

scientific-bounty-deadline-fairness-guard/README.md

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+# Scientific Bounty Deadline Fairness Guard
+
+Focused slice for SCIBASE issue #18, Scientific Bounty System.
+
+This module evaluates deadline extensions, timezone cutoffs, late submissions, and solver notice parity before a scientific bounty challenge proceeds to arbitration or award release. It is intentionally narrower than general intake, scoring, payout routing, evidence freeze, anonymous review packets, or post-closeout retention.
+
+## What it checks
+
+- Challenge deadlines are timezone-explicit and normalized before submission decisions are made.
+- Sponsor deadline extensions are approved, published, and scoped to all eligible solver teams.
+- Every eligible team receives the same new deadline inside the configured notice SLA.
+- Submissions received after the original deadline are accepted only when a valid public extension covers them.
+- Submissions received after the current deadline are rejected or held for arbitration if they were accepted.
+- Evidence-freeze windows are reopened with a new snapshot instead of mutating the original frozen record.
+
+## Local verification
+
+```bash
+node scientific-bounty-deadline-fairness-guard/test.js
+node scientific-bounty-deadline-fairness-guard/demo.js
+node scientific-bounty-deadline-fairness-guard/make-demo-video.js
+```
+
+Generated reviewer artifacts are written to `scientific-bounty-deadline-fairness-guard/reports/`.
+
+## Safety
+
+The fixtures are synthetic. The module does not call payment processors, use private challenge data, touch credentials, or perform any external write action.

scientific-bounty-deadline-fairness-guard/demo.js

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+const fs = require("fs");
+const path = require("path");
+const { challenges } = require("./sample-data");
+const { evaluateChallenges, renderMarkdownReport, renderSvgReport } = require("./index");
+
+function ensureDir(dir) {
+  fs.mkdirSync(dir, { recursive: true });
+}
+
+function runDemo() {
+  const report = evaluateChallenges(challenges);
+  const reportDir = path.join(__dirname, "reports");
+  ensureDir(reportDir);
+
+  fs.writeFileSync(path.join(reportDir, "deadline-fairness-review.json"), `${JSON.stringify(report, null, 2)}\n`);
+  fs.writeFileSync(path.join(reportDir, "deadline-fairness-review.md"), renderMarkdownReport(report));
+  fs.writeFileSync(path.join(reportDir, "deadline-fairness-summary.svg"), renderSvgReport(report));
+
+  console.log("deadline fairness demo generated");
+  console.log(`decision summary: ${JSON.stringify(report.summary)}`);
+  console.log(`reports: ${reportDir}`);
+}
+
+runDemo();