Add demo reset helper for seeded issues

exercises/README.md

@@ -5,6 +5,10 @@ module in the [walkthrough](../docs/walkthrough.md) and maps to a ready‑made G
 [`seed-issues.md`](seed-issues.md). Reference solutions are in [`solutions.md`](solutions.md) —
 don't peek until you've let the agent try.
 
+If you want to reset the demo repository after a run-through, see
+[`demo-reset.md`](demo-reset.md). It preserves the seeded practice issues and removes extra
+issues and pull requests.
+
 `main` ships **green** (8 passing tests). Every exercise asks the agent to add behavior *and* the
 tests that prove it.
 

exercises/demo-reset.md

@@ -0,0 +1,36 @@
+# Reset the demo state
+
+Use this helper to clean up the repository after you have finished a walkthrough or want to start over with a fresh set of practice issues and pull requests.
+
+## What it preserves
+
+The script preserves the four seeded exercise issues from [`seed-issues.md`](seed-issues.md) by matching their titles exactly. Everything else is treated as demo clutter and reset.
+
+## Prerequisites
+
+- GitHub CLI installed and authenticated (`gh auth login`)
+- Run the command from the repository you want to reset
+
+## Preview the changes
+
+```bash
+node scripts/reset-demo.mjs
+```
+
+The script runs in dry-run mode by default and prints the issues and pull requests it would close or delete.
+
+## Apply the reset
+
+```bash
+node scripts/reset-demo.mjs --apply
+```
+
+This will:
+
+- preserve the seeded exercise issues
+- close any extra issues that are still open
+- delete extra issues
+- close any extra pull requests that are still open
+- delete extra pull requests
+
+> The reset is destructive for extra issues and pull requests. Review the dry-run output carefully before using `--apply`.

scripts/reset-demo.mjs

@@ -0,0 +1,89 @@
+#!/usr/bin/env node
+
+import { spawnSync } from 'node:child_process';
+import { existsSync, readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+
+const args = new Set(process.argv.slice(2));
+const apply = args.has('--apply');
+const repoRoot = process.cwd();
+const gitRoot = runGitCommand(['rev-parse', '--show-toplevel'], repoRoot).trim();
+const repo = runGhCommand(['repo', 'view', '--json', 'nameWithOwner', '--jq', '.nameWithOwner'], gitRoot).trim();
+const seededTitles = readSeededIssueTitles(resolve(gitRoot, 'exercises', 'seed-issues.md'));
+
+console.log(`Repository: ${repo}`);
+console.log(`Preserving seeded issues: ${seededTitles.join(', ')}`);
+console.log(apply ? 'Applying changes.' : 'Dry run only. Re-run with --apply to make changes.');
+
+const issues = listIssues(repo);
+const pullRequests = listPullRequests(repo);
+
+const extraIssues = issues.filter((issue) => !seededTitles.includes(issue.title));
+const extraPullRequests = pullRequests;
+
+if (extraIssues.length === 0 && extraPullRequests.length === 0) {
+  console.log('Nothing to reset.');
+  process.exit(0);
+}
+
+for (const issue of extraIssues) {
+  const action = issue.state === 'OPEN' ? `close issue #${issue.number}` : `delete issue #${issue.number}`;
+  if (apply) {
+    if (issue.state === 'OPEN') {
+      runGhCommand(['issue', 'close', String(issue.number), '--repo', repo]);
+    }
+    runGhCommand(['issue', 'delete', String(issue.number), '--repo', repo, '--yes']);
+  }
+  console.log(`${apply ? 'Applied' : 'Would'} ${action}: ${issue.title}`);
+}
+
+for (const pr of extraPullRequests) {
+  const action = pr.state === 'OPEN' ? `close pull request #${pr.number}` : `delete pull request #${pr.number}`;
+  if (apply) {
+    if (pr.state === 'OPEN') {
+      runGhCommand(['pr', 'close', String(pr.number), '--repo', repo]);
+    }
+    runGhCommand(['pr', 'delete', String(pr.number), '--repo', repo, '--yes']);
+  }
+  console.log(`${apply ? 'Applied' : 'Would'} ${action}: ${pr.title}`);
+}
+
+function runGitCommand(args, cwd = repoRoot) {
+  const result = spawnSync('git', args, { cwd, encoding: 'utf8' });
+  if (result.status !== 0) {
+    throw new Error(result.stderr.trim() || `git ${args.join(' ')} failed`);
+  }
+  return result.stdout;
+}
+
+function runGhCommand(args, cwd = repoRoot) {
+  const result = spawnSync('gh', args, { cwd, encoding: 'utf8' });
+  if (result.status !== 0) {
+    throw new Error(result.stderr.trim() || `gh ${args.join(' ')} failed`);
+  }
+  return result.stdout;
+}
+
+function readSeededIssueTitles(seedFilePath) {
+  if (!existsSync(seedFilePath)) {
+    throw new Error(`Seed issues file not found: ${seedFilePath}`);
+  }
+
+  const content = readFileSync(seedFilePath, 'utf8');
+  const titles = [...content.matchAll(/--title\s+"([^"]+)"/g)].map((match) => match[1]);
+  if (titles.length === 0) {
+    throw new Error(`No seeded issue titles found in ${seedFilePath}`);
+  }
+
+  return titles;
+}
+
+function listIssues(repo) {
+  const output = runGhCommand(['issue', 'list', '--state', 'all', '--limit', '1000', '--repo', repo, '--json', 'number,title,state']);
+  return JSON.parse(output);
+}
+
+function listPullRequests(repo) {
+  const output = runGhCommand(['pr', 'list', '--state', 'all', '--limit', '1000', '--repo', repo, '--json', 'number,title,state']);
+  return JSON.parse(output);
+}