Purging one's own app config fragments by config name is not available yet

## Objective

Record that removing one's own app config fragment by config name does not exist on the merged code, so a behaviour test run does not report it as a defect.

## Background

The my app-config-fragment group reads and writes by config name but offers no delete: a caller must resolve the fragment id first and then use the top-level purge. The implementation is in flight as BA-7185, stacked on BA-7183 and BA-7184; this entry exists only to scope the test run and closes when that stack lands.

## Acceptance Criteria

- The behaviour test run treats the missing my purge as known, not as a failure.
- This issue closes once BA-7185 merges and the command answers on a live manager.

## Related

- BA-7185 - the SDK and CLI for the name-addressed purge (the implementation).
- BA-7183, BA-7184 - the service and REST layers it stacks on.

## Story Points

0.5

JIRA Issue: BA-7232

Start with the behaviour test run described in the issue and review how the my app-config-fragment purge is recorded as a known gap. BA-7185 is the implementation, stacked on BA-7183 and BA-7184; done means the live manager answers the name-addressed purge and the issue can close after that stack lands.

Written by the indexing model from the issue text.