fix(bpmn): keep a top-level call activity's fire-and-forget flag through the document PUT

[sfmskywalker]

Closes #8075. Part of #7909.

Problem

A top-level callActivity authored as fire-and-forget (vw:waitForCompletion="false") lost that flag on every PUT bpmn/definitions/{id}/document. In Bpmn.Interchange 0.2.0 the flag lives only on the reader's BpmnWorkBinding.CallProcess, and the BpmnDefinitions document cannot carry it. The PUT wrote top-level content without reusing stored bindings, so re-import bound a waiting call. Studio's Performed-by panel PUTs the whole document on any binding edit, so editing an unrelated task was enough to change runtime behaviour silently.

Fix: option 2, reuse the stored call options

This mirrors how #8077 reuses kept-subprocess bindings. ImportDocumentAsync reads and parses the stored BPMN source once (ReadStoredSource) and passes the result to both reuse helpers. For each top-level call activity in the posted document, it reuses the stored CallProcess binding, re-keyed to the posted element's bindingRef, only when:

• the element id matches, and
• calledElement is unchanged.

A changed calledElement, or a removed or retyped element, binds fresh with the default waiting behaviour, so nothing a client deliberately changed is brought back. CallProcess carries no other options besides CalledElement and WaitForCompletion, so nothing is dropped. A posted call activity without a bindingRef is skipped rather than refused, since the worst case is the pre-existing default rather than data loss. Without that skip the writer would throw on a null key.

There is no contract change: the GET shape, the ETag and the codes are the same, so Studio (elsa-workflows/elsa-studio#1031, #1033) is unaffected.

Tests

• The D4 round-trip gains top-level-call-activity.bpmn: GET, PUT unchanged, export, and the flag is still false.
• Editing another task's binding keeps the flag.
• A changed calledElement binds fresh.
• A call activity without a bindingRef is skipped.
• The no-op PUT ETag-stability theory includes the new fixture, and the ETag stays stable.
• Mutation-tested: disabling the reuse, the calledElement check, or the null-bindingRef guard each turns its test red.
• Local runs:
  • Elsa.Bpmn.UnitTests: 30/30
  • Elsa.Bpmn.Interchange.UnitTests: 14/14
  • Elsa.Bpmn.IntegrationTests: 59/59
  • Elsa.Bpmn.Interchange.IntegrationTests: 108/108

The wiki documents the guarantee next to the "Nested scopes" section.

🤖 Generated with Claude Code

[greptile-apps]

Confidence Score: 5/5

Safe to merge.

Summary

• This change preserves a top-level BPMN call activity’s stored fire-and-forget option when an unrelated document edit is saved. It reads the stored BPMN source once, reuses call options only when the call activity’s element ID and target remain unchanged, adds focused round-trip and endpoint coverage, and documents the behavior.

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