feat(art): replace all 72 posts' artwork with the v2 pipeline

Every post now carries one unique local-ComfyUI/Ideogram 4 base frame, composited
into EN + ZH share cards, a banner and list thumbs.

- the shipped prompts_catalog held only 21 distinct metaphors for 72 posts (16
  shared one visual), so all 72 were rewritten as unique object+state metaphors
  and 10 frames re-rolled after OCR found pseudo-text rendered at legible size
- render_from_art.mjs emits JPEG by default (558 KB PNG -> 84 KB mozjpeg q85);
  the ZH 1200x630 card did not exist before this batch
- 288 frontmatter fields migrated; the 144 v1 PNGs are gone
- PostList's thumb helper keys off the base slug (a ZH card is zh-<slug>.jpg while
  the thumb is <slug>-800.webp, which 404'd the whole ZH listing)
- [...slug].astro's <picture> regex accepts .jpg
- the repo now carries the art inputs (metaphors.json, captions/<slug>.json,
  refreshed prompts_catalog.json) so a frame is reproducible from git alone

scripts/og-gen/captions/every-player-stuttered-the-file-was-fine.json

@@ -0,0 +1 @@
+{"high_level_description":"A dark-mode 3D cyber-bento concept art and technical blueprint schematic of a single piece of industrial hardware. The main high-detail 3D focal subject is positioned strictly on the right side of the canvas, leaving expansive clean dark negative space across the entire left side.","style_description":{"aesthetics":"modern dark cyber-bento, industrial precision, sleek machined surfaces, raytraced ambient occlusion","lighting":"volumetric studio rim lighting in royal cobalt blue (#4d82ff) with vibrant emerald green (#4ade80) status indicator lights and subtle cyan glow","medium":"3d_render","art_style":"octane render, matte obsidian hardware, frosted acrylic glass, technical blueprint vector lines","color_palette":["#0B0F19","#111827","#1E293B","#4ADE80","#3FB950","#4D82FF"]},"compositional_deconstruction":{"background":"Deep midnight obsidian slate background (#0b0f19 to #111827) fading into pure clean negative space across the entire left 60% of the horizontal canvas, with faint technical blueprint grid crosshairs and delicate vector coordinate lines.","elements":[{"type":"obj","bbox":[150,550,850,945],"desc":"A perfectly aligned dark film canister whose internal sprocket teeth sit one notch out of phase, casting a doubled ghost frame onto a translucent projection screen. Clean unbranded matte surfaces, blank panels, no printed markings. Razor-sharp detail, no text, no letters, no watermark."}]}}