Geothermal has long been the clean, firm power source that was always a few breakthroughs away from being cheap enough to matter. Numbers buried in a Nevada utility filing suggest that day may have arrived. Joel Edwards, co-founder and CTO of geothermal developer Zanskar, put it bluntly earlier this month: "to all the geothermal believers out there, the flippening has come." In NV Energy's 2026 resource plan, three geothermal offers came in at $105 to $107 per megawatt-hour. That's below the roughly $114/MWh capacity-weighted average for the 11…