add multi-sink diagnostic log; make framebuffer optional

src/boot/efi.zig

@@ -34,7 +34,15 @@ fn boot() !noreturn {
     // Everything the kernel needs must be gathered *before* we exit boot
     // services, since afterwards none of these calls are usable.
     var boot_info: BootInfo = .{
-        .framebuffer = try queryFramebuffer(bs),
+        // A missing GOP (a headless machine) is not fatal — hand the kernel a
+        // "no framebuffer" descriptor (base 0) and let it log to serial instead.
+        .framebuffer = queryFramebuffer(bs) catch danos.Framebuffer{
+            .base = 0,
+            .width = 0,
+            .height = 0,
+            .pitch = 0,
+            .format = .bgrx,
+        },
         .memory_map = undefined, // filled by exitBootServices, just below
         .kernel_segments = undefined, // filled by loadKernel
         .kernel_segment_count = 0,