Saviour? Leader of Plaid Cymru, Rhun ap Iorwerth. (Photo by Ryan Jenkinson/Getty Images) There is a type of political upheaval that changes everything on the surface but very little underneath. Yesterday’s Senedd result has the makings of just such an upheaval.  Welsh Labour’s century of dominance has ended, which is the kind of statement that will animate history PhDs, commentators and a certain type of political obsessive for years to come. Pub quizmasters must be thrilled to have a new question: who was the first leader of a government in the UK to lose their seat while in office? (Eluned Morgan). The explanations, though, are not hugely complex. Twenty-seven years running the devolved government without making Wales richer and more prosperous. Stubbornly staying put in Old Labour comfort zones, opposing school and public service reforms purely because they carried Tony Blair’s fingerprints.…