feat: draw a sharing card per platform page

Each platform page shares a card titled with the platform's name, rendered by make_og_cards.py --only platforms.

scripts/make_og_cards.py

@@ -5,40 +5,76 @@ Each card is an SVG written by ``sitediagrams.og_card_svg`` from the
 registry, rasterised by a headless Chromium through Playwright, then
 committed under ``docs_assets/og/``. The site build copies the PNG files and
 never runs this script, so it adds nothing to the build's dependencies.
-Run it again when a section's wording or the platform count changes.
+Run it again when a section's wording, the platform count or the list of
+platforms changes.
 
     python scripts/make_og_cards.py
+    python scripts/make_og_cards.py --only platforms
+
+A platform page shares a card with its own name (``og/platforms/<id>.png``),
+the other pages their section's.
 """
 
 from __future__ import annotations
 
+import argparse
 import sys
 from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
 sys.path.insert(0, str(ROOT / "scripts"))
 
+from common import list_registered_platforms, load_platform_config  # noqa: E402
 from sitediagrams import OG_SECTIONS, og_card_svg  # noqa: E402
 
 OUT = ROOT / "docs_assets" / "og"
 LOGO = ROOT / ".github" / "assets" / "logo.png"
+PLATFORM_TAGLINE = "Which BIOS files it needs, and where each one goes"
+
+
+def platform_cards() -> dict[str, str]:
+    """Each platform page's card, by its path under og/, with its title."""
+    platforms = ROOT / "platforms"
+    return {
+        f"platforms/{name}": load_platform_config(name, str(platforms))["platform"]
+        for name in list_registered_platforms(str(platforms), include_archived=True)
+    }
+
+
+def card_svg(key: str, logo: bytes, titles: dict[str, str]) -> str:
+    if key in OG_SECTIONS:
+        return og_card_svg(key, logo)
+    # A platform card is a section card with the platform's name for title.
+    OG_SECTIONS[key] = (titles[key], PLATFORM_TAGLINE)
+    try:
+        return og_card_svg(key, logo)
+    finally:
+        del OG_SECTIONS[key]
 
 
 def main() -> None:
+    parser = argparse.ArgumentParser(description="Render the sharing cards to PNG.",
+                                     allow_abbrev=False)
+    parser.add_argument("--only", choices=("sections", "platforms"),
+                        help="render one kind of card (default: both)")
+    args = parser.parse_args()
     try:
         from playwright.sync_api import sync_playwright
     except ImportError as exc:
         raise SystemExit("Playwright with Chromium is needed: pip install playwright") from exc
-    OUT.mkdir(parents=True, exist_ok=True)
+    titles = platform_cards()
+    keys = [*([] if args.only == "platforms" else OG_SECTIONS),
+            *([] if args.only == "sections" else titles)]
     logo = LOGO.read_bytes()
     with sync_playwright() as playwright:
         browser = playwright.chromium.launch()
         page = browser.new_page(viewport={"width": 1200, "height": 630})
-        for section in OG_SECTIONS:
+        for key in keys:
             page.set_content(
-                '<html><body style="margin:0">' + og_card_svg(section, logo) + "</body></html>"
+                '<html><body style="margin:0">' + card_svg(key, logo, titles) + "</body></html>"
             )
-            path = OUT / f"{section}.png"
+            path = OUT / f"{key}.png"
+            path.parent.mkdir(parents=True, exist_ok=True)
             page.screenshot(path=str(path), clip={"x": 0, "y": 0, "width": 1200, "height": 630})
             print(path.relative_to(ROOT))
         browser.close()