fix(ci): resolve clippy neg_multiply warnings and commit .nvmrc

- Fix clippy::neg_multiply warnings across dynamical systems and ODE tests
- Track and commit .nvmrc and rust-toolchain.toml for GitHub Actions workflows

Author: namvdo

.nvmrc

@@ -0,0 +1 @@
+22.12.0

rust-toolchain.toml

@@ -0,0 +1,5 @@
+[toolchain]
+channel = "1.81.0"
+components = ["clippy", "rustfmt"]
+profile = "minimal"
+targets = ["wasm32-unknown-unknown"]

src/continuous_ds.rs

@@ -535,7 +535,7 @@ mod tests {
         let val = ode.vector_field(pos).unwrap();
 
         assert!((val.x - (2.0 * 0.5 - 2.0)).abs() < 1e-12);
-        assert!((val.y - (-1.5 * -2.0)).abs() < 1e-12);
+        assert!((val.y - (1.5 * 2.0)).abs() < 1e-12);
     }
 
     #[test]
@@ -620,8 +620,8 @@ mod tests {
         let pos = Vector2::new(2.0, -1.0);
         let val = ode.vector_field(pos).unwrap();
 
-        assert!((val.x - (1.1 * 2.0 + -0.3 * -1.0 + 0.7)).abs() < 1e-12);
-        assert!((val.y - (2.0 * 2.0 + -1.5 * -1.0)).abs() < 1e-12);
+        assert!((val.x - (1.1 * 2.0 + 0.3 * 1.0 + 0.7)).abs() < 1e-12);
+        assert!((val.y - (2.0 * 2.0 + 1.5 * 1.0)).abs() < 1e-12);
     }
 
     #[test]

src/dynamical_systems.rs

@@ -362,8 +362,8 @@ mod tests {
         let pos = Vector2::new(2.0, -1.0);
         let result = system.map(pos).unwrap();
 
-        assert!((result.x - (1.5 * 2.0 + -0.25 * -1.0 + 0.75)).abs() < 1e-12);
-        assert!((result.y - (-2.0 * 2.0 + 3.0 * -1.0)).abs() < 1e-12);
+        assert!((result.x - (1.5 * 2.0 + 0.25 * 1.0 + 0.75)).abs() < 1e-12);
+        assert!((result.y - (-2.0 * 2.0 - 3.0 * 1.0)).abs() < 1e-12);
     }
 
     #[test]

src/user_defined.rs

@@ -174,6 +174,6 @@ mod tests {
         let (x_out, y_out) = eq.eval(0.5, -2.0).unwrap();
 
         assert!((x_out - (2.0 * 0.5 - 2.0)).abs() < 1e-12);
-        assert!((y_out - (-1.0 * -2.0)).abs() < 1e-12);
+        assert!((y_out - (1.0 * 2.0)).abs() < 1e-12);
     }
 }