feat(core,cli): harden install engine and extend skill lint and interview eval

- update only touches the recorded project root; project installs do not
  follow symlinks or junctions; repeated --force rotates .orig backups;
  uninstall never deletes outside the recorded root
- run npm/npx without a shell on Windows and pin optional tool versions
- skip the update check in CI and non-interactive output
- lint: cross-document section pointers, preflight row ids, gate rule
  numbers, per-document size budgets, gate copy equality
- eval: scenarios S19-S21, route and read-cost rejudging, interpretation
  card judging, temp-dir previews and table-form cards no longer fail

build/eval/interview/fixtures/s19-code-language-no-design-md/styles/site.css

@@ -0,0 +1,10 @@
+@import url("tokens.css");
+body { margin: 0; background: var(--color-bg); color: var(--color-ink); font-family: var(--font-body); line-height: 1.7; }
+.nav { display: flex; gap: var(--space-4); padding: var(--space-4) var(--space-8); border-bottom: 1px solid var(--color-line); }
+.nav a { color: var(--color-ink); text-decoration: none; }
+.page { max-width: 60rem; margin: 0 auto; padding: var(--space-16) var(--space-8); }
+h1, h2 { font-family: var(--font-display); font-weight: 700; line-height: 1.25; }
+h1 { font-size: 2.5rem; margin: 0 0 var(--space-4); }
+.lede { color: var(--color-ink-muted); max-width: 34em; }
+.button { display: inline-block; padding: var(--space-2) var(--space-4); background: var(--color-accent); color: #fff; border-radius: var(--radius-control); text-decoration: none; }
+.feature { padding: var(--space-8) 0; border-top: 1px solid var(--color-line); }