Preserve inheritance split and cast-action microflow roundtrips

[hjotha]

Part of #332. Staged in draft PR #346.

Summary

Some microflows contain structured InheritanceSplit and CastAction shapes. The current describer/builder path can lose type-split structure, cast outputs, or branch continuation behavior when those actions are nested inside other control-flow constructs.

Expected behavior

describe -> exec -> describe should preserve:

• structured inheritance split branches by target type;
• cast-object actions and their output variables;
• nested split/cast branches inside IF/loop bodies;
• branch joins and terminal branches without corrupting the roundtripped MPR.

Current staging status

The local all-fixes branch contains support in draft PR #346, but it is coupled to other flow-graph fixes. Extract into one or more focused PRs after isolating the minimum shared traversal helpers.

Validation target

Focused PR should include synthetic unit tests for nested inheritance/cast control flow and pass make build, make lint-go, and make test.

[github-actions]

Issue Triage

Summary:
The issue requests that mxcli’s describe‑exec‑describe roundtrip preserve inheritance‑split and cast‑action microflow structures, especially when nested inside other control‑flow constructs.

Checklist (feature request):

• ✅ Use case / problem statement – provided
• ✅ Proposed syntax or behavior – provided (describe → exec → describe should preserve the listed elements)
• ❌ Mendix version relevance – not specified

Request for missing information:
Could you let us know which Mendix version(s) this change is relevant for (e.g., 9.x, 10.x, or all versions)? This helps us prioritize and test the fix appropriately. Thank you!

---

Automated triage via OpenRouter — workflow source