fix: add missing toolchain parameter to security workflow

- Add 'toolchain: stable' to dtolnay/rust-toolchain action
- Remove continue-on-error from cargo-deny since deny.toml is configured
- Fixes workflow parsing error that caused immediate failure

Author: joshrotenberg

.github/workflows/security.yml

@@ -33,6 +33,8 @@ jobs:
 
       - name: Install Rust
         uses: dtolnay/rust-toolchain@7b1c307e0dcbda6122208f10795a713336a9b35a  # stable
+        with:
+          toolchain: stable
 
       - name: Cache cargo registry
         uses: Swatinem/rust-cache@82a92a6e8fbeee089604da2575dc567ae9ddeaab  # v2.7.5
@@ -89,7 +91,6 @@ print(json.dumps(sarif))
         with:
           command: check
           arguments: --all-features
-        continue-on-error: true  # Don't fail until deny.toml is configured
 
   dependency-review:
     name: Dependency Review