Summary

• CI failure on main (tests/middleware.test.ts > Middleware > middleware runs even on not found routes) was caused by the previous +not-found static-probe shortcut bailing to null before middleware ran.
• Now the shortcut still bypasses the page render, but routes through runMiddlewares first when the matched +not-found has middleware — middleware can intercept (e.g. JSON 404), otherwise we return a bare 404 instead of SSR'ing the not-found page.
• Routes with no middleware still get the cheap return null path so the unit test for sourcemap probes is unaffected.

Test plan

• packages/one vitest passes (20/20 in createHandleRequest, 518/574 overall)
• CI: full tests/test dev + prod suites green (the integration middleware test was the failure)