Business plan: isometric calculator views instead of FreeCAD, software section with screenshots

- Cover and section 6.2 now use the isometric plant view of the plant and
  business plan calculator, drawn with each version's own preset: the
  cover (roofs, no labels), Figure 8 the site from above, Figure 9 the
  ground floor cut open, Figure 10 the press hall close up. The FreeCAD
  aerial render, the Mueang Chi site plan and the hall layout sketch are
  no longer in the plan; the captions say the calculator draws the Payap
  scenario model while the 6.2 text and zone table are the Mueang Chi
  hall.
- New section 5.5 "The software: plant overview, factory console and
  artist platform" with six screenshots of the demos: the plant overview
  (simulated SCADA), the factory console press floor and its ERPNext
  link, the artist ordering offer, fan funding and the record passport.
  Simulated data is marked as such; the platform name stays undecided.
- Figures renumbered (budget card 11, cash 12) and named in the
  section 15 source table. Renders in docs/renders/calculator/ and
  docs/renders/demos/; README bullet updated.

docs/business-plan/build/content_a.py

@@ -17,7 +17,7 @@ def blocks():
         title="What It Takes to Build a Top-Notch Vinyl Plant",
         subtitle="Business plan for a full-service vinyl, cassette and CD manufacturing plant "
                  "in the Chiang Mai region, Northern Thailand",
-        image="renders/aerial-hero.png",
+        image=pick("renders/calculator/plan-a-cover.png", "renders/calculator/plan-b-cover.png"),
         lines=[
             "**Prepared for:** the project's lead investor",
             "**Prepared by:** Simona Meesaiyati (Project Lead) and Alexander Grabowski (Technical Consultant), "
@@ -34,7 +34,9 @@ def blocks():
                  "This version is Plan B: the whole chain, cutting and galvanics included, with five presses "
                  "at launch and everything in, at ~225M THB (~224M). A second version, Plan A (~180M THB), "
                  "launches with three presses and six cost levers. ")
-             + "The plan price includes the ramp-up reserve and carries no contingency. Draft 0.3 replaces "
+             + "The plan price includes the ramp-up reserve and carries no contingency. Cover picture: the "
+             "plant as the plant and business plan calculator draws this plan (schematic, Payap scenario "
+             "layout, section 6.2). Draft 0.3 replaces "
              "draft 0.2 (October 2026), which described a single launch plant priced with a contingency.",
     ))
     out.append(TOC())