QUEUE-144: Source branch for split Wire context-listener PRs [do not merge]

[peter-lawrey]

Source branch only - do not merge

This draft is the original QUEUE-144 source branch. Review and merge the split PR stack instead:

1. QUEUE-144: Add document context count contract #1270 - int DocumentContext.contextCount() and ProgressiveContext.
2. QUEUE-144: Add marshallable output context listener API #1271 - shared context-listener API.
3. QUEUE-144: Implement wire context listener lifecycle #1272 - Wire listener lifecycle.
4. QUEUE-144: Support context listeners in marshallable outputs #1273 - concrete MarshallableOut adapters.
5. QUEUE-144: Document wire context listener contract #1274 - contract documentation.

The branch is retained as provenance for the extracted commits and any remaining assurance comparison. It is currently 0 commits behind develop, but it combines all five review units and should not be used as the release path.

Commit 18647d0b2 mirrors the reviewed #1270 representation by keeping contextCount() as an int. Supported context identifiers, including Queue roll cycles, are inherently int-valued; Queue consumers should depend on the split stack rather than this umbrella.

Validation of the latest source-branch correction

• mvn -q -o -Dtest=DocumentContextLifecycleTest,MarshallableOutContextListenerTest test - pass.
• /usr/bin/time -p mvn -q -o clean verify - pass in 42.71 seconds.
• git diff --check - pass.