Switch rehype-mermaid to client-side rendering to fix Astro 6 OOM

[Copilot]

Astro 6 migration caused OOM during website builds. Root cause: rehype-mermaid defaults to inline-svg strategy, which launches a headless Playwright/Chromium browser at build time to server-side render diagrams. Combined with Astro 6's higher baseline memory, this exceeded limits. There is exactly one mermaid diagram in the entire site.

Changes

• website/astro.config.mjs: Switch rehype-mermaid to pre-mermaid strategy (no browser spawn). Add conditional client-side mermaid.js loader that only fetches the library on pages with diagrams:

  [rehypeMermaid, { strategy: "pre-mermaid" }]

• website/package.json: Remove NODE_OPTIONS="--max-old-space-size=8192" workaround from build:web

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/bin/astro.mjs build sh tool�� ebsite/src/conte--llmstxt node pec/node_modules../../website/src/content/docs/docs/emitters/openapi3/reference ld.json && pnpm node grep /.bin/node sh /nod�� node scripts/generate-version.js sh de_modules/pnpm/dist/node-gyp-bin/sh ental ture tools/pnpm/10.30doc node (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Investigate astro 6 extra memory usage</issue_title>
<issue_description>Migrating to astro 6 caused OOM error, increasing to 8GB solve the issue but maybe we should investigate why and if we can reduce that</issue_description>

<agent_instructions>Investiage if there is something in the ./website setup that would cause this out of memory error, might need to revert the change to the build script to insrease the memory</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Investigate astro 6 extra memory usage #10051

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