media: Update to zig 0.16.0, harden tests and add test build step

packages/media/src/jpeg.zig

@@ -20,6 +20,10 @@ const Info = union(enum) {
     pub fn makeFull(full: Header) Info {
         return .{ .full = full };
     }
+
+    test "refAllDecls" {
+        std.testing.refAllDecls(@This());
+    }
 };
 
 const Header = struct {
@@ -107,6 +111,10 @@ const Marker = enum(u8) {
             self == .EOI or
             self == .TEM;
     }
+
+    test "refAllDecls" {
+        std.testing.refAllDecls(@This());
+    }
 };
 
 /// The caller asserts that the buffer is at least `format.magic_length` bytes
@@ -137,3 +145,7 @@ pub fn info(buffer: []const u8) ?Info {
 
     @panic("TODO");
 }
+
+test "refAllDecls" {
+    std.testing.refAllDecls(@This());
+}