next.js

15109c16 - Decouple loader tree construction from children ordering (#97192)

Decouple loader tree construction from children ordering (#97192) ## Summary The app loader tree currently mutates Turbopack's parallel route map to ensure `children` is inserted first. This makes the loader tree representation depend on a compatibility ordering that only matters when the tree is emitted as JavaScript. This keeps the generated loader tree unchanged while moving `children`-first ordering to the Turbopack code generator. The output continues to preserve the rendering order added for head and CSS handling during client navigation, while consumers of the internal tree select `children` by key. ## Verification - `pnpm build-all` <!-- NEXT_JS_LLM -->