Interactive figures in Risks, Governance, and Evaluations chapters show infinite loading spinner

[Sappique]

Several "Interactive figure" embeds across chapters 2, 4, and 5 never load — the loading spinner animates indefinitely and no iframe ever appears in the DOM.

Affected pages (15 figures total):

/chapters/v1/risks/risk-decomposition (1)
/chapters/v1/risks/misalignment-risks (1)
/chapters/v1/risks/systemic-risks (2)
/chapters/v1/risks/risk-amplifiers (1)
/chapters/v1/risks/appendix-forecasting-scenarios (2)
/chapters/v1/governance/compute-governance (2)
/chapters/v1/governance/systemic-challenges (2)
/chapters/v1/governance/governance-architectures (2)
/chapters/v1/evaluations/benchmarks (2)

Example: https://ai-safety-atlas.com/chapters/v1/evaluations/benchmarks/ — figures 5.1 and 5.2 show "Loading..." indefinitely.

Root cause:

The page HTML contains the figure's caption and spinner, but no <iframe> element. In src/components/nodes/Iframe.astro, the iframe is only rendered when src is truthy — the spinner is unconditional, so when src is empty the user sees a permanent loading state.

The src comes from the Iframe component tables in the chapter Google Docs, via convertIframe in transformer.ts:339-344, which reads attrs.src. The affected chapter docs (Risks, Governance, Evaluations) use a row named "source" instead of "src" — so attrs.src is undefined and the iframe never gets a URL. Chapter 1 uses "src" and renders fine.

Suggested fix:

Either standardize the Google Docs to use "src" consistently, or make the transformer accept both "src" and "source" as the attribute name.