ISR fallback shells served for prefetch requests

Misc Changes

• Serve ISR fallback shells in response to prefetch requests: #94534
• Insights: drop irrelevant fix cards from instant errors: #94926
• Navigation inspector UI updates: #94959
• skill(next-cache-components-adoption): clarify prereqs: #95082
• Turbopack: Delete dead AttachedFileSystem type: #94960
• Opt Partial Prefetching routes into the runtime stage of Cached Navs: #95097
• Fix #95015 by pulling a fix to scattered-collect: #95098
• docs(caching): clarify generateStaticParams prebuild and recommend max for CMS: #95081
• Release the instant navs lock without clearing the whole cookie jar: #94947
• Compute dev fallback params from the most-specific prerendered route: #95066

Credits

Huge thanks to @acdlite, @aurorascharff, @samselikoff, @bgw, @unstubbable, @lukesandberg, and @icyJoseph for helping!