det ports: a LINKed program's COMMAREA writes are lost when it abends (caBack runs only on normal return) #4534

Problem

In det ports, a LINKed program's COMMAREA writes are copied back to the caller only on a normal RETURN (caBack runs only then). In CICS, a local LINK passes the caller's COMMAREA by reference, so every write the linked program made before it abended is still visible to the caller, whether the caller handles the abend (HANDLE ABEND / a handler program) or reads it afterwards.

Evidence

Found by the #4528 worker (PR #4533). The cics-crucible case hc-abend-link sub-unhandled fails because HCSUB's COMMAREA writes are not seen by the caller after HCSUB abends. The other 4 hc-abend-link scenarios pass.

Acceptance criteria

• A local LINK's COMMAREA writes are visible to the caller after the linked program abends, on the det port (and on the generator's region façade if it shares the path).
• hc-abend-link sub-unhandled passes on the det port; no regression on cics_crucible --ci (pinned) or the det sweep.
• Distributed program link (remote) semantics stay out of scope; refuse by name if a case needs them.

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