Runtime Prefetch Runs For Every Dynamic Render, And A Prefetch Export Cannot Opt A Route Out

The condition in server/app-render/app-render.js (lines 475 and 2003) is `if (Boolean(renderOpts.partialPrefetching) || await anySegmentHasPartialPrefetchingEnabled(tree))`. Because the first operand short-circuits when the global flag is true, the code never checks whether the route's segment configuration explicitly disables runtime prefetch. The function `anySegmentHasPartialPrefetchingEnabled` only detects opt-in values ('partial', 'unstable_eager'), so an opt-out cannot be expressed.

1. Clone https://github.com/damianfrizzi/next-runtime-prefetch-repro 2. Run `bun install` 3. Run `./run-all.sh` 4. Observe the output table: rows with partialPrefetching true and no opt-out have 2 copies in Flight; partialPrefetching false has 1 copy. The row with prefetch='force-disabled' still has 2 copies.

This change alters the conditions under which runtime prefetch is generated. Routes that previously relied on the global flag and had no explicit opt-out will continue to spawn prefetch, but routes with `prefetch='auto'` may now stop spawning if `auto` is treated as an opt-out; verify that this matches the intended semantics for auto. The new tree traversal adds a small per-render overhead. Because this is an internal Next.js patch, it is tightly coupled to app-render.js internals and may break after upgrading to a newer version; apply the same change only to the exact versions listed. Rollback: revert the two condition replacements and delete the new helper functions. Test with representative routes under partialPrefetching true, especially those using searchParams and multiple parallel routes.