Enable revive linter, and fix a bunch of warnings

I took the set of enabled checks from revive's recommended configuration [1],
and removed some that I didn't like. There might be other useful checks in
revive that we might want to enable, but this is a nice improvement already.

The bulk of the changes here are removing unnecessary else statements after
returns, but there are a few others too.

[1] https://github.com/mgechev/revive?tab=readme-ov-file#recommended-configuration

pkg/tasks/tasks_test.go

@@ -167,7 +167,7 @@ func (d *BlankLineReader) Read(p []byte) (n int, err error) {
 		return 0, io.EOF
 	}
 
-	d.linesYielded += 1
+	d.linesYielded++
 	p[0] = '\n'
 	return 1, nil
 }