Bundle SDL runtime with Windows builds

[Confetti3]

Summary

• copy SDL3.dll beside Windows binaries from the Cargo build script
• make CI validate the automatic runtime bundling instead of copying the DLL manually
• leave Diagnostic Freeze disabled for newly created scenes

Verification

• cargo fmt --all --check
• cargo build --profile dist --locked --no-default-features --bin alkahest-prebl
• confirmed lib/SDL3.dll and target/dist/SDL3.dll have identical SHA-256 hashes
• target/dist/alkahest-prebl.exe --version (without PATH modification)
• cargo test --workspace --all-targets --locked --no-default-features (99 passed, 1 ignored)