Preserve nested branch tails and split-join continuations

[hjotha]

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

Summary

Nested splits can have guarded tails, empty branch joins, partial joins, or branch-local case/anchor state that the describer/builder currently cannot always pair back to the right continuation.

Expected behavior

Roundtrip should preserve:

• guarded branch tails that continue after nested joins;
• validation-feedback targets that are variables rather than attribute paths;
• nested merge fallback when a child split has no directly paired merge;
• split joins that converge at a non-merge activity;
• branch case/anchor state when leaving a nested split.

Current staging status

Draft PR #346 contains the implementation, but it is split across several historical commits and needs focused extraction. Some pieces may need to wait for shared traversal helpers to land first.

Validation target

Focused PRs should include synthetic tests for guarded tails, variable validation feedback targets, and nested split join fallback, then pass make build, make lint-go, and make test.

[github-actions]

Issue Triage

Summary:
The issue requests enhancements to mxcli so that round‑trip processing preserves nested split‑join constructs such as guarded tails, variable‑based validation targets, and branch‑local case/anchor state.

Checklist for feature request

Required info	Present?	Notes
Use case – why the feature is needed / what problem it solves	❌	Implied but not explicitly stated.
Proposed syntax or behavior (if applicable)	⚠️	Expected behavior is listed, but a concrete proposal (e.g., CLI flag, config change) is missing.
Mendix version relevance (if version‑specific)	❌	No mention of which Mendix versions are affected.

Request for clarification
Could you please add:

1. A brief description of the use case (e.g., the kind of Mendix projects or MDL scripts where this loss occurs and why preserving these details matters).
2. Any specific proposal for how the feature should be exposed (e.g., a new option, default behavior change, or configuration).
3. Whether this applies to all Mendix versions or only certain releases (e.g., 9.x, 10.x).

Once those details are added, the issue will be ready for implementation. Thanks for contributing!

---

Automated triage via OpenRouter — workflow source