improvise-m6op: the cross-instance fixture carries measure_agg entries, so its sort is pinned

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

context/test-evidence/command.md

@@ -227,6 +227,14 @@ checked by adding a `probe_field` to `Model` and to `Model::new`. The build then
 failed with `E0027: pattern does not mention field probe_field` at the `Debug`
 impl, and nowhere else.
 
+**`Model.measure_agg` needed the same treatment (improvise-m6op).** `Model`'s
+`Debug` sorts `measure_agg` through a `BTreeMap`, but the fixture's
+`measure_agg` was empty, so nothing saw the sort. With the sort replaced by the
+raw `HashMap` (`.field("measure_agg", &measure_agg)`), this test stayed green in
+3 of 3 runs. The fixture now carries four entries: `Revenue` Avg, `Cost` Min,
+`Units` Max and `Orders` Count. Under the same injection it is red in 3 of 3
+runs, and it is green with the sort restored.
+
 ### a_stale_wire_model_command_cannot_be_applied
 
 A wire `Command::Model` cannot reach the document without its basis being checked