fix(ci): contracts build/test now fail CI, fix inconsistent Rust toolchain

- Remove continue-on-error from contracts build and test steps so failures are not silently ignored

- Fix gas-comparison job to use toolchain 1.85.0 instead of stable for consistency with all other Rust jobs

Author: ebenezershadrack123-star

.github/workflows/ci.yml

@@ -23,11 +23,9 @@ jobs:
           toolchain: 1.85.0
 
       - name: Build contracts
-        continue-on-error: true
         run: cd contracts && cargo build --lib
 
       - name: Run contract tests
-        continue-on-error: true
         run: cd contracts && cargo test
 
       - name: Run gas benchmarks
@@ -213,7 +211,7 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@stable
         with:
-          toolchain: stable
+          toolchain: 1.85.0
 
       - name: Run benchmarks on base (main)
         run: |