@remotion/cli: Add Config.setRspack()

[JonnyBurger]

Summary

• add Config.setRspack() as the canonical config-file API
• keep Config.setExperimentalRspackEnabled() as a deprecated compatibility alias
• rename the CLI flag to --rspack
• reject --experimental-rspack with a migration error
• replace the experimental Studio warning with a verbose log of the selected bundler
• update the Rspack documentation and test coverage

Closes #9786.

Testing

• focused CLI and renderer option tests
• manual CLI checks for --rspack and --experimental-rspack
• bun run build
• bun run stylecheck
• bun run prewarm-twoslash in packages/docs
• bun test src in packages/docs
• bun run build-docs in packages/docs
• bun run render-cards in packages/docs

Red/green verified for the new config setter and the removed CLI flag error.

Preview

• Configuration file
• Webpack and Rspack
• Studio CLI
• Render CLI
• Still CLI
• Bundle CLI
• Benchmark CLI
• Lambda deploySite()
• Cloud Run deploySite()

[vercel]

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Project	Deployment	Actions	Updated (UTC)
bugs	Ready	Preview, Comment	Jul 29, 2026 1:33pm
remotion	Ready	Preview, Comment	Jul 29, 2026 1:33pm

[pullfrog]

✅ No new issues found.

Reviewed changes — adds Config.setRspack() as the canonical config-file API, keeps Config.setExperimentalRspackEnabled() as a deprecated compatibility alias, and migrates docs and the example to the new name.

• Add Config.setRspack() to the config type and Config object — both setRspack and setExperimentalRspackEnabled route to rspackOption.setConfig.
• Mark setExperimentalRspackEnabled() as @deprecated in the JSDoc with a link to the new API.
• Update docs — config.mdx now documents setRspack() as the primary API and shows the old name with strikethrough and a deprecation callout; overwriting-webpack-config.mdx uses the new API in its snippet.
• Update remotion.config.ts in the example to use Config.setRspack(true).
• Add test verifying both APIs configure the same option value.

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