Pin the Node toolchain, remove runtime npm repair, make CI and E2E truthful

Phase 0 of the improvement plan (ai_prompts/prompt4.md): make the baseline
reproducible and stop the test runner from masking real failures.

- Pin Node >= 22.12 (engines + .nvmrc + engine-strict); every entry point
  fails fast with clear guidance instead of dying late with ERR_REQUIRE_ESM
  inside the packaging dependency graph.
- electron-launcher.js is diagnostics-only: all runtime npm install/rebuild/
  repair paths are removed. npm ci on the pinned toolchain is the only
  supported install path (README + GETTING_STARTED updated).
- Refuse to silently launch unsandboxed on Linux: --no-sandbox now requires
  an explicit STEPFORGE_ALLOW_NO_SANDBOX/ELECTRON_DISABLE_SANDBOX opt-in and
  is otherwise a hard error with actionable fixes; user-namespace sandboxing
  is detected and preferred.
- Click-capture E2E no longer converts startup crashes into "SKIPPED": the
  only allowed skip is the upfront absence of a display server. A missing
  shared library or crash now fails with the startup log. Same guard added
  to the startup smoke check.
- GitHub CI: run on pull_request, pin Node from .nvmrc, drop the macOS matrix
  entry (not a support target), and audit production and full dependency
  trees as separate signals. Gitea CI: pull_request trigger + pinned Node.
- Refresh package-lock on Node 22/npm 10 and remediate the form-data and
  undici advisories (npm audit: 0 vulnerabilities, prod and full tree).
- Stop tracking generated machine-specific build reports
  (build/build_report.md, build/artifacts_manifest.json).

Verified: 203 unit tests pass; repo-structure, startup-smoke, unit-workflows,
sample-artifacts, and build-release checks pass locally with a real Electron
launch. The click self-test now truthfully reports the pre-existing Linux
arm/debounce capture failures (also red on Gitea CI main run 177) instead of
hiding behind SKIPPED; that defect is scheduled for the capture-fix PR.

Co-Authored-By: Claude Fable 5 <[email protected]>

scripts/check-node-version.js

@@ -0,0 +1,79 @@
+'use strict';
+
+// Hard prerequisite check for the supported Node toolchain.
+//
+// The locked dependency graph (notably the electron-builder packaging
+// toolchain) requires Node >= 22.12. Older Nodes fail late with confusing
+// errors (ERR_REQUIRE_ESM deep inside dependencies) instead of a clear
+// message, so every entry point calls this first.
+
+const fs = require('node:fs');
+const path = require('node:path');
+
+function parseVersion(version) {
+  const match = /^v?(\d+)\.(\d+)\.(\d+)/.exec(String(version).trim());
+  if (!match) return null;
+  return [Number(match[1]), Number(match[2]), Number(match[3])];
+}
+
+function compareVersions(a, b) {
+  for (let i = 0; i < 3; i += 1) {
+    if (a[i] !== b[i]) return a[i] < b[i] ? -1 : 1;
+  }
+  return 0;
+}
+
+function requiredNodeVersion(projectRoot = path.join(__dirname, '..')) {
+  const pkg = JSON.parse(fs.readFileSync(path.join(projectRoot, 'package.json'), 'utf8'));
+  const range = pkg.engines && pkg.engines.node ? String(pkg.engines.node) : null;
+  if (!range) return null;
+  const match = /(\d+\.\d+\.\d+)/.exec(range);
+  return match ? match[1] : null;
+}
+
+function checkNodeVersion({
+  currentVersion = process.versions.node,
+  projectRoot = path.join(__dirname, '..'),
+} = {}) {
+  const required = requiredNodeVersion(projectRoot);
+  if (!required) return { ok: true, required: null, current: currentVersion };
+
+  const current = parseVersion(currentVersion);
+  const minimum = parseVersion(required);
+  if (!current || !minimum) return { ok: true, required, current: currentVersion };
+
+  return {
+    ok: compareVersions(current, minimum) >= 0,
+    required,
+    current: currentVersion,
+  };
+}
+
+function assertSupportedNode(options = {}) {
+  const result = checkNodeVersion(options);
+  if (result.ok) return result;
+
+  const message = [
+    `StepForge requires Node ${result.required} or newer; this is Node ${result.current}.`,
+    '',
+    'Install the pinned toolchain (see .nvmrc) and reinstall dependencies:',
+    '',
+    '  nvm install && nvm use    # or install Node 22 LTS another way',
+    '  npm ci',
+    '',
+    'Older Nodes fail unpredictably inside the packaging dependency graph,',
+    'so this check stops early instead.',
+  ].join('\n');
+
+  const error = new Error(message);
+  error.code = 'STEPFORGE_UNSUPPORTED_NODE';
+  throw error;
+}
+
+module.exports = {
+  assertSupportedNode,
+  checkNodeVersion,
+  compareVersions,
+  parseVersion,
+  requiredNodeVersion,
+};