fix: resolve CI linting failures

- Removed unused imports (pathlib.Path, Schema, EnvVar, Optional)
- Fixed f-strings without placeholders in generator.py and validators.py
- Removed unused variables in generator.py
- Updated CI workflow to use correct project name (envschema)

envschema/validators.py

@@ -41,7 +41,7 @@ class IntegerValidator:
             return True, None
         except ValueError:
             return False, ValidationError(
-                f"Invalid integer value",
+                "Invalid integer value",
                 value=value
             )
 
@@ -62,7 +62,7 @@ class BooleanValidator:
         if value_lower in BooleanValidator.FALSE_VALUES:
             return True, None
         return False, ValidationError(
-            f"Invalid boolean value (expected: true, false, 1, 0, yes, no, on, off)",
+            "Invalid boolean value (expected: true, false, 1, 0, yes, no, on, off)",
             value=value
         )
 
@@ -77,7 +77,7 @@ class ListValidator:
         if "," in value:
             return True, None
         return False, ValidationError(
-            f"Invalid list value (expected comma-separated values)",
+            "Invalid list value (expected comma-separated values)",
             value=value
         )