loader: rework kernel entry point

src/kern/init.zig

@@ -11,6 +11,9 @@ var thread0: ke.Thread = undefined;
 export fn kmain(boot_info: *r.BootInfo) callconv(.c) void {
     r.boot_info = boot_info;
 
+    // Immediately initialize the context of what will eventually become
+    // our idle thread. We keep running on the loader stack up until we switch
+    // into the thread.
     thread0.init(
         boot_info.kernel_stack,
         boot_info.kernel_stack_size,

src/kern/thread.zig

@@ -137,7 +137,12 @@ pub const Thread = struct {
         arg: ?*anyopaque,
     ) void {
         thread.* = .{
-            .context = .init(stack, stack_size, entry, arg),
+            .context = .init(
+                stack,
+                stack_size,
+                entry,
+                arg,
+            ),
             .lock = .init(),
             .nice = 0,
             .priority = prio,