build: update KosmicKrisp which now requires macOS 26

The new Mesa revision builds KosmicKrisp with the precompiled shader
compiler, and the driver now needs macOS 26 (and the aligned iOS,
tvOS, and visionOS 26 releases) at runtime. Bump the availability
gates on the settings picker and the VM start check to match.

Assisted-by: Claude:claude-fable-5-1

Platform/macOS/SettingsView.swift

@@ -256,7 +256,7 @@ struct DisplaySettingsView: View {
                     Text("Default").tag(UTMQEMUVulkanDriver.qemuVulkanDriverDefault)
                     Text("Disabled").tag(UTMQEMUVulkanDriver.qemuVulkanDriverDisabled)
                     Text("MoltenVK").tag(UTMQEMUVulkanDriver.qemuVulkanDriverMoltenVK)
-                    if #available(macOS 15, *) {
+                    if #available(macOS 26, *) {
                         Text("KosmicKrisp").tag(UTMQEMUVulkanDriver.qemuVulkanDriverKosmicKrisp)
                     }
                 }.help("Select the Vulkan driver to use for host passthrough rendering. Vulkan requires guest drivers to be installed.")