fix(template): fix interior mutability issue by formalizing the hash function

Author: lalvarezt

src/pipeline/template.rs

@@ -983,6 +983,32 @@ impl Display for MultiTemplate {
     }
 }
 
+/// Hash implementation based only on the template string content.
+///
+/// This implementation ignores interior mutability in parsed operations and
+/// caches, making it safe to use MultiTemplate as a key in hash collections.
+/// Two templates with the same string content will always hash equally.
+impl Hash for MultiTemplate {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.raw.hash(state);
+    }
+}
+
+/// Equality implementation based only on the template string content.
+///
+/// Two templates are considered equal if they have the same raw template string,
+/// regardless of their internal state or cached operations.
+impl PartialEq for MultiTemplate {
+    fn eq(&self, other: &Self) -> bool {
+        self.raw == other.raw
+    }
+}
+
+/// Equivalence relation implementation.
+///
+/// Required for use as keys in hash collections. Based on template string equality.
+impl Eq for MultiTemplate {}
+
 /* ---------- backward compatibility alias --------------------------------- */
 
 /// Type alias for backward compatibility.