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

packages/media/src/qoa.zig

@@ -22,6 +22,10 @@ const Header = union(enum) {
     pub fn initStatic(static: HeaderStatic) Header {
         return .{ .static = static };
     }
+
+    test "refAllDecls" {
+        std.testing.refAllDecls(@This());
+    }
 };
 
 const HeaderStreaming = void;
@@ -36,6 +40,10 @@ const HeaderStatic = struct {
         const sample_rate: f64 = @floatFromInt(self.sample_rate);
         return @floatCast(samples / sample_rate);
     }
+
+    test "refAllDecls" {
+        std.testing.refAllDecls(@This());
+    }
 };
 
 /// The caller asserts that the buffer is at least `format.magic_length` bytes
@@ -73,3 +81,7 @@ pub fn info(buffer: []const u8) ?Header {
         });
     }
 }
+
+test "refAllDecls" {
+    std.testing.refAllDecls(@This());
+}