- expansion runs last at the sinks, never in payload transforms
- only the exact placeholder serialization expands; stable across calls
- the Go policy negatives are stripped the same way in the mirror
- htmlGate.ts mirrors the four editor-output rules of the Go policy:
figure data-embed (^youtube$) and data-id (^[A-Za-z0-9_-]{11}$),
img alt with any text, ol start (integer)
- embeds.ts: EMBED_PROVIDERS (youtube on youtube-nocookie.com),
EMBED_PLACEHOLDER and expandEmbeds
- JournalPostBody and JournalCategoryHeader render
expandEmbeds(sanitizeJournalHtml(html)); payload transforms only sanitize
- .journal-embed styles (16 / 9 block, borderless iframe)
- tests: byte copy of the editor corpus, mirror and pipeline cases;
acme hello-acme carries a placeholder and the SSR smoke checks the iframe
- README Embeds section and decision note Policy amendment
