Make a record: investor demo of the artist platform, end-user flow

New static page docs/make-a-record.html (test site /demos/make-a-record/):
the artist platform as a customer would see it, polished for presenting.

- five steps (design, music and art, price, fan funding, track) with a
  sticky stage: to-scale mock-up (record spins at 33 1/3 or 45 rpm on
  hover), spec chips, price per copy, ship month and the next action
- design as option cards and swatches; options that do not apply stay
  visible and disabled (weight and gatefold off 12", colour pickers for
  black vinyl)
- masters and artwork read in the browser as in the detailed demo, side
  bars per side, checks in plain words, approval 1 of 3
- price with the curve, itemised lines folded under one summary, lead time
  as two bars (approvals, then the 7 to 9 week quote)
- fan funding: goal, break-even and what the artist keeps, money rules;
  the campaign on a phone with a pre-order ticker, funded or missed ends,
  production timeline with the artist's approvals, updates feed
- record passport for one delivered copy (stamper, press, cycle time and
  side; stage dates; optical inspection and sampled audio), per
  traceability.md and quality-automation.md, IDs simulated; repress card
- "Investor notes" switch with the business case per step (market
  research, vault, short-run economics and the Thai price gap, plant-owned
  vs broker and the Qrates lesson, traceability and represses); guided
  tour of about a minute (#tour, #notes in the URL)
- light/dark theme shared with the other pages; phone layout with a
  bottom bar

Same price list (demo-0.1) and stage table as artist-order.html, so the
defaults reproduce the artist platform example: 37,836 THB per title,
232 THB per copy at 100, break-even 41, goal 100, 548 THB kept a copy.

artist-platform.md: investor demo paragraph. traceability.md: the record
passport as the per-copy customer view. README bullet and layout line,
site DEMOS line and landing-page entry.

site/public/index.html

@@ -103,6 +103,17 @@ document.documentElement.setAttribute("data-theme",t);})();
         demand against installed capacity.</span>
       </a>
     </li>
+    <li>
+      <a href="demos/make-a-record/">
+        <strong>Make a record (investor demo)</strong>
+        <span>The artist platform as a customer sees it: design a record
+        against a to-scale mock-up, check the music and artwork, see one
+        clear price, let fans fund the pressing, follow production through
+        the artist approvals and open the record passport of one delivered
+        copy. Switch on investor notes for the business case behind each
+        step, or press Tour for a one-minute walk-through.</span>
+      </a>
+    </li>
     <li>
       <a href="demos/artist-order/">
         <strong>Artist ordering and fan funding</strong>