feat: build-time OpenGraph images (satori-free, resvg + vendored TTFs)

- one 1200x630 PNG per page per locale, design-system styled
- hand-built SVG rasterised by resvg (handles variable fonts; satori cannot)
- vendored Space Grotesk / Inter / JetBrains Mono TTFs for deterministic offline builds

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitattributes

@@ -10,6 +10,8 @@
 *.pdf binary
 *.woff binary
 *.woff2 binary
+*.ttf binary
+*.otf binary
 *.ico binary
 
 # Shell scripts and container files must stay LF even on Windows checkout.

site/src/pages/og/[image].png.ts

@@ -0,0 +1,76 @@
+import type { APIRoute } from 'astro';
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import { Resvg } from '@resvg/resvg-js';
+import { PAGE_IDS, type PageId } from '@i18n/slugMap';
+import { LOCALES, type Locale } from '@i18n/locales';
+import { getProfile, getMeta } from '@lib/content';
+
+/*
+  Build-time OpenGraph images (SEO_SPEC §4): one per page per locale, styled in the
+  design system (dark surface, name, role line, trace motif, monogram + page tag).
+  The SVG is hand-built (the design is simple and fully controlled) and rasterised by
+  resvg, which handles the vendored variable TTFs via its own font DB — satori's
+  opentype parser cannot read variable fonts.
+  Fonts read from the project source (cwd = site/ at build).
+*/
+
+const fontBuffers = ['SpaceGrotesk.ttf', 'Inter.ttf', 'JetBrainsMono.ttf'].map((n) =>
+  readFileSync(resolve(process.cwd(), 'src/assets/og-fonts', n)),
+);
+
+export function getStaticPaths() {
+  const paths: { params: { image: string }; props: { pageId: PageId; locale: Locale } }[] = [];
+  for (const pageId of PAGE_IDS) {
+    for (const locale of LOCALES) {
+      paths.push({ params: { image: `${pageId}-${locale}` }, props: { pageId, locale } });
+    }
+  }
+  return paths;
+}
+
+const esc = (s: string) =>
+  s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+
+export const GET: APIRoute = ({ props }) => {
+  const { pageId, locale } = props as { pageId: PageId; locale: Locale };
+  const profile = getProfile(locale);
+  const roleLine = profile.roleLine;
+  const tag = pageId === 'home' ? '' : (getMeta(pageId, locale).title.split(' · ')[0] ?? '');
+  const tagW = Math.min(tag.length * 15 + 44, 1000);
+
+  const svg = `<svg width="1200" height="630" viewBox="0 0 1200 630" xmlns="http://www.w3.org/2000/svg">
+  <rect width="1200" height="630" fill="#0B0E14"/>
+  <rect x="64" y="64" width="52" height="52" rx="12" fill="#11151D" stroke="#5C6675"/>
+  <text x="90" y="99" font-family="JetBrains Mono" font-size="22" font-weight="700" fill="#E8ECF2" text-anchor="middle">CB</text>
+  <text x="134" y="98" font-family="JetBrains Mono" font-size="20" fill="#9AA4B2">cesnimda.co.uk</text>
+
+  <text x="64" y="330" font-family="Space Grotesk" font-size="80" font-weight="600" fill="#E8ECF2" letter-spacing="-1">${esc(profile.name)}</text>
+  <text x="64" y="382" font-family="Inter" font-size="30" fill="#9AA4B2">${esc(roleLine)}</text>
+
+  <rect x="64" y="420" width="240" height="2" fill="#3ECFAE"/>
+  <path d="M304 421 l12 12 H420" fill="none" stroke="#3ECFAE" stroke-width="2"/>
+  <circle cx="424" cy="433" r="5" fill="#3ECFAE"/>
+
+  ${
+    tag
+      ? `<rect x="64" y="500" width="${tagW}" height="48" rx="24" fill="none" stroke="#3ECFAE"/>
+  <text x="${64 + tagW / 2}" y="530" font-family="JetBrains Mono" font-size="22" fill="#3ECFAE" text-anchor="middle">${esc(tag)}</text>`
+      : `<text x="64" y="530" font-family="JetBrains Mono" font-size="22" fill="#5C6675">systems developer · tønsberg, norway</text>`
+  }
+</svg>`;
+
+  const png = new Resvg(svg, {
+    fitTo: { mode: 'width', value: 1200 },
+    font: { fontBuffers, loadSystemFonts: false, defaultFontFamily: 'Inter' },
+  })
+    .render()
+    .asPng();
+
+  return new Response(png, {
+    headers: {
+      'Content-Type': 'image/png',
+      'Cache-Control': 'public, max-age=31536000, immutable',
+    },
+  });
+};