wasm: update Surfer artifact SHA256 to match current GitLab build

The Surfer artifact was updated upstream; update the locked SHA256 to
the new value so setup-surfer.sh passes verification.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: thomasahle

scripts/toolchain.lock.sh

@@ -11,4 +11,4 @@ readonly CIRCT_REF_LOCKED="6334424eee194b21b9b33148742071e8201fbbc2"
 readonly CIRCT_LLVM_SUBMODULE_REF_LOCKED="972cd847efb20661ea7ee8982dd19730aa040c75"
 
 readonly SURFER_ARTIFACT_URL_LOCKED="https://gitlab.com/surfer-project/surfer/-/jobs/artifacts/main/download?job=pages_build"
-readonly SURFER_ARTIFACT_SHA256_LOCKED="f2dc43c1b735394e4b153d55bddcad843dade5e39dbfdd0757270e68d19d0fe8"
+readonly SURFER_ARTIFACT_SHA256_LOCKED="a8eba2eba26d6a2bc34dd6c347b65ebbc10acbfbb31769f2bf091f4f97f01814"