Remove ostruct dependency

[BenTopping]

Changes:

• Prefer pry-byebug over pry-nav
  • pry-nav pins pry to versions containing ostruct (<0.15)
  • pry-nav also has not received updates in > 5 years.
• Remove ostruct
  • This gem has no runtime dependency on ostruct, only via pry < 0.15.

Context

Ostruct was recently added as a dependency but I don't think it needs to be. I raised a comment on the original pr but did not receive a reply.
I don't actively work on this repository so please let me know if the pry-byebug substitution is reasonable. Let me know if you have any questions or require any changes.

[kerrizor]

Hey @BenTopping! 👋

First off, I apologize for not responding to your comment on #435 back in June — that was an oversight on my part.

You're absolutely right on all counts here. I went back and checked: there's literally zero usage of OpenStruct anywhere in the rails-erd library code. The deprecation warning I was trying to fix in #435 was coming from pry (via pry-nav), not from rails-erd itself. I should have traced the actual source of the warning instead of just adding a runtime dependency to silence it.

Your fix is the correct approach:

• ✅ Removes an unnecessary runtime dependency that was being pulled into every project using rails-erd
• ✅ Updates pry-nav → pry-byebug (actively maintained vs 5+ years stale)
• ✅ Addresses the root cause rather than papering over it

The .pryrc with the command aliases is a nice touch too — preserves the familiar s/n/f/c shortcuts.

I'll get this merged. Thanks for taking the time to investigate and submit the fix! 🎉