Misc Changes

• [ci] Add an TURBO_TASKS_AVAILABLE_PARALLELISM environment variable that overrides std::thread::available_parallelism callsites: #93995
• Make --debug-build-paths work with src/ directory projects: #94016
• ci: run Linux Playwright jobs in prebuilt Microsoft container: #93794
• Revert "Prerender HTTP access fallbacks with Cache Components semantics": #94018
• Respond to App Shell prefetches on the server: #93998
• [turbopack] Disable ctor under RA: #94022
• Upgrade rustc to nightly-2026-05-15: #94021
• Turbopack: don't crash the dev server when node_modules/next is briefly unresolvable: #93877
• Include PPR routes in dynamicRoutes regardless of revalidate time: #94025
• Enable experimental.varyParams by default: #94010
• Enable experimental.optimisticRouting by default: #94011
• Enable experimental.cachedNavigations by default with cacheComponents: #94012
• Update font data: #94006
• [ci] Set TURBO_TASKS_AVAILABLE_PARALLELISM to 4 in most e2e tests: #93996

Credits

Huge thanks to @bgw, @unstubbable, @timneutkens, @acdlite, @lukesandberg, @mischnic, @gnoff, and @vercel-release-bot for helping!