Add challenge solver withdrawal continuity guard

challenge-solver-withdrawal-continuity-guard/README.md

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+# Solver Withdrawal Continuity Guard
+
+Self-contained Scientific Bounty System slice for issue #18. It evaluates active solver/team withdrawals or replacements after a private challenge workspace has opened, before milestone review, sponsor scoring, payout, or IP handoff continues.
+
+## What It Checks
+
+- Dated withdrawal notice records.
+- Workspace access revocation after a solver leaves.
+- Solver IP return, retention, or destruction confirmation.
+- Team quorum and eligible replacement readiness.
+- Artifact custody for work owned by withdrawing solvers.
+- Near-term milestone risk after team membership changes.
+- Sponsor and reviewer notification coverage.
+
+## Outputs
+
+- `reports/withdrawal-continuity-packet.json`: structured decisions, findings, summaries, and actions.
+- `reports/coordinator-packet.md`: readable challenge coordinator packet.
+- `reports/summary.svg`: visual decision summary.
+- `reports/demo.mp4`: short demo artifact for Algora review.
+
+## Local Verification
+
+```bash
+node --test challenge-solver-withdrawal-continuity-guard/test.js
+node challenge-solver-withdrawal-continuity-guard/demo.js
+node --check challenge-solver-withdrawal-continuity-guard/index.js
+node --check challenge-solver-withdrawal-continuity-guard/sample-data.js
+node --check challenge-solver-withdrawal-continuity-guard/demo.js
+node --check challenge-solver-withdrawal-continuity-guard/test.js
+```
+
+The module is dependency-free, uses synthetic data only, and makes no network calls. Set `FFMPEG_PATH` to an ffmpeg binary before running `demo.js` if regenerating `reports/demo.mp4`.

challenge-solver-withdrawal-continuity-guard/demo.js

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+const fs = require('node:fs');
+const path = require('node:path');
+const {spawnSync} = require('node:child_process');
+
+const {
+  evaluateSolverWithdrawalContinuity,
+  buildCoordinatorPacket,
+} = require('./index');
+const {scenarios} = require('./sample-data');
+
+const reportsDir = path.join(__dirname, 'reports');
+const framesDir = path.join(reportsDir, 'frames');
+fs.mkdirSync(reportsDir, {recursive: true});
+
+const evaluations = scenarios.map((scenario) => ({
+  scenario: scenario.name,
+  ...evaluateSolverWithdrawalContinuity(scenario),
+}));
+
+const decisionCounts = evaluations.reduce((counts, item) => {
+  counts[item.decision] = (counts[item.decision] || 0) + 1;
+  return counts;
+}, {});
+const findings = evaluations.reduce((sum, item) => sum + item.findings.length, 0);
+const affectedTeams = evaluations.reduce((sum, item) => sum + item.summary.affectedTeams, 0);
+const readyReplacements = evaluations.reduce((sum, item) => sum + item.summary.replacementsReady, 0);
+
+const packetJson = JSON.stringify(evaluations, null, 2);
+const coordinatorPacket = evaluations.map(buildCoordinatorPacket).join('\n---\n');
+const svg = `<svg xmlns="http://www.w3.org/2000/svg" width="960" height="540" viewBox="0 0 960 540">
+  <rect width="960" height="540" fill="#111827"/>
+  <text x="48" y="70" fill="#f8fafc" font-family="Arial, sans-serif" font-size="32" font-weight="700">Solver Withdrawal Continuity Guard</text>
+  <text x="48" y="110" fill="#bfdbfe" font-family="Arial, sans-serif" font-size="18">Challenge continuity packet for solver withdrawals, replacements, and artifact custody</text>
+  <g transform="translate(48 156)">
+    <rect width="260" height="148" rx="8" fill="#7f1d1d"/>
+    <text x="24" y="46" fill="#fee2e2" font-family="Arial, sans-serif" font-size="20" font-weight="700">Workspace Hold</text>
+    <text x="24" y="108" fill="#fef2f2" font-family="Arial, sans-serif" font-size="56" font-weight="700">${decisionCounts['hold-workspace-continuity'] || 0}</text>
+  </g>
+  <g transform="translate(350 156)">
+    <rect width="260" height="148" rx="8" fill="#92400e"/>
+    <text x="24" y="46" fill="#fef3c7" font-family="Arial, sans-serif" font-size="20" font-weight="700">Coordinator Review</text>
+    <text x="24" y="108" fill="#fffbeb" font-family="Arial, sans-serif" font-size="56" font-weight="700">${decisionCounts['coordinator-review'] || 0}</text>
+  </g>
+  <g transform="translate(652 156)">
+    <rect width="260" height="148" rx="8" fill="#166534"/>
+    <text x="24" y="46" fill="#dcfce7" font-family="Arial, sans-serif" font-size="20" font-weight="700">Continuity Ready</text>
+    <text x="24" y="108" fill="#f0fdf4" font-family="Arial, sans-serif" font-size="56" font-weight="700">${decisionCounts['continuity-ready'] || 0}</text>
+  </g>
+  <text x="48" y="372" fill="#e5e7eb" font-family="Arial, sans-serif" font-size="22">Affected teams: ${affectedTeams} | Ready replacements: ${readyReplacements} | Findings: ${findings}</text>
+  <text x="48" y="416" fill="#d1d5db" font-family="Arial, sans-serif" font-size="18">Checks: notice, access revocation, IP return, team quorum, artifact custody, milestone risk, notifications</text>
+  <text x="48" y="470" fill="#9ca3af" font-family="Arial, sans-serif" font-size="16">Synthetic data only. No credentials, private challenge files, payout actions, KYC, bank, or live workspace calls.</text>
+</svg>
+`;
+
+fs.writeFileSync(path.join(reportsDir, 'withdrawal-continuity-packet.json'), `${packetJson}\n`);
+fs.writeFileSync(path.join(reportsDir, 'coordinator-packet.md'), coordinatorPacket);
+fs.writeFileSync(path.join(reportsDir, 'summary.svg'), svg);
+
+function fillRect(buffer, width, x0, y0, rectWidth, rectHeight, color) {
+  const [r, g, b] = color;
+  const x1 = Math.min(width, x0 + rectWidth);
+  const y1 = Math.min(Math.floor(buffer.length / (width * 3)), y0 + rectHeight);
+  for (let y = Math.max(0, y0); y < y1; y += 1) {
+    for (let x = Math.max(0, x0); x < x1; x += 1) {
+      const offset = (y * width + x) * 3;
+      buffer[offset] = r;
+      buffer[offset + 1] = g;
+      buffer[offset + 2] = b;
+    }
+  }
+}
+
+function writePpmFrame(filePath, frameIndex, frameCount) {
+  const width = 640;
+  const height = 360;
+  const buffer = Buffer.alloc(width * height * 3);
+  for (let i = 0; i < width * height; i += 1) {
+    buffer[i * 3] = 17;
+    buffer[i * 3 + 1] = 24;
+    buffer[i * 3 + 2] = 39;
+  }
+  const progress = frameIndex / Math.max(1, frameCount - 1);
+  fillRect(buffer, width, 42, 42, 556, 44, [248, 250, 252]);
+  fillRect(buffer, width, 42, 112, 160, 118, [127, 29, 29]);
+  fillRect(buffer, width, 240, 112, 160, 118, [146, 64, 14]);
+  fillRect(buffer, width, 438, 112, 160, 118, [22, 101, 52]);
+  fillRect(buffer, width, 42, 266, Math.round(556 * progress), 28, [191, 219, 254]);
+  fillRect(buffer, width, 42 + Math.round(492 * progress), 310, 64, 26, [248, 250, 252]);
+  const header = Buffer.from(`P6\n${width} ${height}\n255\n`);
+  fs.writeFileSync(filePath, Buffer.concat([header, buffer]));
+}
+
+function createDemoVideo() {
+  const ffmpegPath = process.env.FFMPEG_PATH;
+  if (!ffmpegPath) {
+    console.log('FFMPEG_PATH not set; skipped MP4 generation.');
+    return;
+  }
+
+  fs.rmSync(framesDir, {recursive: true, force: true});
+  fs.mkdirSync(framesDir, {recursive: true});
+  const frameCount = 72;
+  for (let index = 0; index < frameCount; index += 1) {
+    writePpmFrame(path.join(framesDir, `frame-${String(index).padStart(3, '0')}.ppm`), index, frameCount);
+  }
+
+  const output = path.join(reportsDir, 'demo.mp4');
+  const result = spawnSync(ffmpegPath, [
+    '-y',
+    '-framerate',
+    '24',
+    '-i',
+    path.join(framesDir, 'frame-%03d.ppm'),
+    '-c:v',
+    'libx264',
+    '-pix_fmt',
+    'yuv420p',
+    '-movflags',
+    '+faststart',
+    output,
+  ], {encoding: 'utf8'});
+
+  fs.rmSync(framesDir, {recursive: true, force: true});
+  if (result.status !== 0) {
+    throw new Error(result.stderr || 'ffmpeg failed to generate demo.mp4');
+  }
+}
+
+createDemoVideo();
+
+console.log(`Wrote ${evaluations.length} solver withdrawal evaluations to ${reportsDir}`);
+console.log(`Decision counts: ${JSON.stringify(decisionCounts)}`);
+console.log(`Affected teams: ${affectedTeams}`);
+console.log(`Ready replacements: ${readyReplacements}`);
+console.log(`Findings: ${findings}`);