feat(web): Pressing Plant component library + describeJob

design.css component classes (masthead, contents nav, tiles, dept header,
job row + severity stripe, status chip, progress bar, pressed list, buttons,
fields). Presentational _ui components. describeJob maps worker Job.state to
literal labels + severity kind + stepped progress (unit-tested).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/_ui/section-header.tsx

@@ -0,0 +1,9 @@
+export function SectionHeader({ title, note }: { title: string; note?: string }) {
+  return (
+    <div className="dept">
+      <h2>{title}</h2>
+      <span className="fill" />
+      {note ? <span className="count">{note}</span> : null}
+    </div>
+  );
+}