v15.4.0-canary.7

Core Changes

• Turbopack: don’t warn about webpack being configured when experimental.turbo is set: #77998
• Upgrade React from bc6184dd-20250417 to 914319ae-20250423: #78468
• Update turbopack to syn2: #78385

Misc Changes

• build: Update mdxjs-rs to v1: #78469
• fix(turbopack): Fix sourcemap path on windows: #78453
• fix(turbo-tasks): Add a few more transient-from-persistent task assertions: #78301
• fix(CI): Reduce Rspack test retries from 2 to 0 to reduce timeouts: #78390
• test: attempt to de-flake graceful shutdown test: #78464
• Fix potential race condition in createRouterAct: #78473

Credits

Huge thanks to @wbinnssmith, @kdy1, @bgw, @lubieowoce, @lukesandberg, and @acdlite for helping!