Catch Exception is too broad in createArchive()

## Bug

`createArchive()` catches `Exception` in its error handling block, which is broader than necessary and can swallow unrelated exceptions.

## Location

`AbstractJarMojo.java:291-294`:

```java
} catch (Exception e) {
// TODO: improve error handling
throw new MojoException("Error assembling JAR", e);
}
```

## Problem

Catching `Exception` will also catch unchecked runtime exceptions (e.g. `NullPointerException`, `ArrayIndexOutOfBoundsException`) and even `Throwable` subtypes like `Error` (though `Error` is not a subclass of `Exception`). The existing `// TODO: improve error handling` comment acknowledges this. Consider narrowing the catch clause to the specific exception types thrown by the operations in the try block.

## Suggested fix

Catch `IOException` and `MavenArchiverException` (or other specific exception types from the archiver API) instead of the generic `Exception`.