Assertion diff output for dicts does not consistently follow insertion order

[anuranjansb]

Hi maintainers 👋

While working on assertion diffs, I noticed that in some cases (especially
nested or wrapped dictionaries), the diff output does not preserve insertion
order, even though Python dicts are ordered.

This can make diffs harder to read and inconsistent across runs.

I explored a possible fix but realized the behavior is tied to how assertion
diffs are constructed internally, and I didn’t want to propose a change without
confirming intent first.

Before working on a PR, I wanted to ask:
• Is preserving insertion order in dict assertion diffs an intended goal?
• Are there known constraints or design reasons for the current behavior?

If this is considered desirable, I’d be happy to work on a minimal and
maintainer-approved fix.

Thanks for your time!