Docs: Move effect previews into packages/docs

[JonnyBurger]

Summary

• move effect preview render compositions from packages/example into packages/docs/src/remotion/Root.tsx under effect-previews
• remove legacy packages/example/src/HtmlInCanvas/effects-*-preview.tsx sources and related Root wiring
• update .agents/skills/add-effect/SKILL.md to require adding preview compositions and rendering them from docs

Verification

• bunx turbo make --filter=docs
• bunx turbo make --filter=@remotion/example
• bun run formatting

[pullfrog]

Pullfrog stalled

The agent stopped emitting events for 303s and was killed by the activity-timeout watchdog. 145 events were processed before the failure.

Recent agent stderr

INFO  2026-05-28T08:28:41 +0ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +59ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +2ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +37ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +1ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +38ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +0ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +53ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +1ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +39ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +1ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +38ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +40ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +41ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:41 +43ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:42 +37ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:42 +48ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:42 +1ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:42 +37ms service=bus type=message.part.delta publishing
INFO  2026-05-28T08:28:42 +1ms service=bus type=message.part.delta publishing

  ^{｜ Rerun failed job ➔ ｜ View workflow run ｜ via Pullfrog ｜ Using Kimi K2 ｜ 𝕏}

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
bugs	Ready	Preview, Comment	May 28, 2026 8:08am
remotion	Ready	Preview, Comment	May 28, 2026 8:08am