Order demos: spine choice, artwork templates, PDF and AI uploads

User request (October 2026): the order tool needs a thin / thick spine
selection, templates for the jacket and label upload, and must accept AI
and PDF files.

Both artist demos (artist-order, make-a-record):
- Spine: thin 3 mm (one record) or thick 5 mm (two records, or a thick
  insert); a double album in a single jacket takes 5 mm, thin is then
  disabled; 7", gatefold (7 or 9 mm) and own jacket disable the row with
  the reason. Quote line 'Thick 5 mm spine' (R.spine 12 / 10 THB per
  copy, estimate from QRP 0.90 vs 0.55 USD and Kudos 137.50 GBP/order).
  Mock-up draws the spine edge to scale; caption names it.
- Templates: vector PDFs written in the browser for the current choice:
  jacket spread (back, spine, front; 633/635 x 315 mm for 12" from
  Mighty Media Discs), gatefold with an inside page, labels with a page
  per side and the dinked hole; trim and bleed boxes set, 3 mm bleed,
  5 mm safe area, folds, crop marks, guidance notes.
- Uploads accept PDF, AI (PDF-compatible) and images. PDFs are read in
  the browser (object streams inflated with DecompressionStream): page
  boxes, pages, PDF/X, creator, colour spaces, font embedding; checks
  against the chosen spine (a 5 mm spread on a 3 mm order is flagged),
  bleed, CMYK, fonts; old PostScript-only AI files are refused with the
  fix. Image spreads are measured the same way. Preview via pdf.js
  (jsDelivr, loaded only when a PDF arrives); the front panel goes into
  the mock-up.

artist-platform.md: new section 'Artwork templates and files' with the
sources; preflight step links it; RI 'left out' list updated. README
demo bullet. Checked headless on Edge: fixtures (3/5 mm spreads, no
bleed, AI, legacy AI, front only, labels, 150 dpi PNG), downloaded
templates parsed with PyMuPDF, 390/1024/1280 px no overflow, dark and
light, no page errors; pw_mr_check --tour and pw_ri unchanged
(37,836 / 232).

docs/artist-platform.md

@@ -131,7 +131,7 @@ covered, and what the demos took from it:
   demo.
 - **Left out for now:** label print modes (CMYK, Pantone, one colour),
   board grades and finishes (kraft, Hansaboard, matt or gloss varnish,
-  laminates), die-cut holes, 6 mm spines, booklets, foil numbering,
+  laminates), die-cut holes, spines other than 3 and 5 mm, booklets, foil numbering,
   sticker position, protective outer sleeves, BIO PVC and a recycled
   colour mix, and multi-address shipping. Each is a price-list line once
   the packaging partner and the compound suppliers quote.
@@ -238,6 +238,44 @@ flags as its biggest open question. The real price list is set after
 market validation ([roadmap](roadmap.md) item 1); the calculator only
 makes whatever prices are chosen legible.
 
+## Artwork templates and files
+
+Decided for the demos (user, October 2026): the order tool offers a
+**spine choice** and **templates to download**, and accepts the files
+designers actually deliver, **PDF and Illustrator (AI)** as well as
+images.
+
+- **Spine.** Thin, 3 mm, holds one record in its inner sleeve; thick,
+  5 mm, holds two, or one with a thick insert or a poster. Plants publish
+  templates for both, and for 7 or 9 mm on a gatefold (Mighty Media Discs:
+  12" sleeve 633 x 315 mm with a 3 mm spine, 635 x 315 mm with 5 mm;
+  Implant: 5 mm for two records; RPM Records: gatefold with a 7 mm spine;
+  XVinylX: 9 mm gatefold; all checked October 2026). A double album in a
+  single jacket takes the 5 mm spine without asking. The thick spine is
+  an extra line on the quote, an estimate until the packaging partner
+  quotes: Quality Record Pressings (US) lists a generic wide-spine jacket
+  at 0.90 USD against 0.55 for a standard one, and Kudos (UK) charges
+  137.50 GBP per order for an extra wide spine (price lists, checked
+  October 2026). A 7" jacket keeps the 3 mm spine.
+- **Templates** follow the format, the jacket type and the spine chosen:
+  the jacket spread (back, spine, front) with 3 mm bleed, a 5 mm safe
+  area and the folds marked, a second page for the inside of a gatefold,
+  and a label template with one page per side (centre hole, and the
+  large hole of a dinked 7"). They are vector PDFs with trim and bleed
+  boxes set, so they open in Illustrator, InDesign and Affinity. Until
+  the packaging partner supplies its dielines the sizes come from the
+  published templates above; 10" and 7" panels are the mock-up's sizes.
+- **Files accepted:** PDF (PDF/X-4 preferred), Illustrator files saved
+  with PDF compatibility (an AI file without it is refused with
+  instructions), and 300 dpi images. Plants ask for the same: Mobineko
+  publishes PSD, AI and PDF templates, New Orleans Record Press takes
+  print PDFs and refuses flattened images (checked October 2026). The
+  preflight reads the page boxes, colour spaces and fonts from the file,
+  checks the trim against the chosen spine (a spread made for a 5 mm
+  spine is flagged on a 3 mm order), the bleed, CMYK against RGB, and
+  whether fonts are embedded or outlined, and renders the front panel
+  into the mock-up.
+
 ## Fan-funded campaigns
 
 ### Before the campaign goes live
@@ -254,7 +292,8 @@ Nothing goes in front of fans that the plant cannot make:
 3. **Automatic artwork preflight**: label and jacket files against the
    templates (size, centre hole and safe area for the pressed-in label,
    bleed, resolution, colour space), with a rendered mock-up of the
-   jacket and the vinyl colour.
+   jacket and the vinyl colour; templates and accepted files in
+   [Artwork templates and files](#artwork-templates-and-files).
 4. **Engineer check**: a cutting engineer confirms side length and level
    are cuttable. On a Sillitoe lathe this is a number from the software's
    virtual groove (disk capacity in percent) without a test cut; see