Schema save creates a duplicate identical version on freshly created projects

[JArmandoAnaya]

On a freshly created project: define classes, press Save version → v1 is created. Press Save version again immediately, with no edits → v2 is created with identical content (the version panel itself renders "Nothing changed between v1 and v2"). Only the third press is caught by the no-change detection ("nothing to save" toast).

Observed only on freshly created projects.

cf. the schema editor design in DESIGN.md ("Versioning is ambient, not modal": Save version is always enabled; pressing it with no changes shows a toast and issues no request).

Reproduction

1. Create a project.
2. Open the Schema tab, add one or more classes.
3. Press Save version → v1.
4. Press Save version again, without editing anything → v2 is created.
5. Press Save version a third time → "No changes to save".

[JArmandoAnaya]

Decision (Armando, 2026-08-14): Saving a schema version whose content is identical to the current active version is a no-op enforced at the kernel level — the service compares the canonical content of the submitted classes against the active version and, when identical, returns the existing active version without creating a new one. "Identical" is defined by the same change-detection logic that already produces the "Nothing changed between vN and vN+1" rendering — one definition of "changed", shared, never two parallel ones. The frontend additionally refreshes its no-change baseline immediately after a successful save, so a repeated press is caught client-side without issuing a request, per DESIGN.md. The kernel comparison is the authoritative guard; the client check is a courtesy. Whether the kernel comparison is implemented as a canonical deep comparison or a content hash is an implementation detail — the requirement is content identity. — supersedes any prior direction