docs/upgrade-classes.md lists upgrade classes (Safe / Caution / Breaking) but doesn't explain what contract changes map to each class

[Timi16]

Backlog source: docs/issues/backlog-100-issues.md
Backlog item: I-034
Section: Section C — Feature Reference Docs (Issues 23–40)
Tag: DOC
Commit context: 9776e85

Observed gap

• docs/upgrade-classes.md (1071 bytes) lists upgrade classes (Safe / Caution / Breaking) but doesn't explain what contract changes map to each class.

Requested outcome

• Turn this backlog item into a concrete repo change in the referenced documentation, tutorial, architecture guide, or contributor workflow.
• Update related cross-links, examples, or adjacent documentation where needed so the change does not leave the docs tree inconsistent.

Completion criteria

• The gap described above is resolved in the repository.
• Any affected docs navigation or contributor guidance remains internally consistent.
• The issue can be closed with a concrete documentation or process change, not just discussion.

[Sam-Rytech]

@Sam-Rytech has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi maintainer

I'd like to take up this issue.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Sam-Rytech to this issue.