mesh-issues: a take-over note records who acted, not the worker named; tests for the remaining rules (hq issue 399)

The note's by is who acted as the runtime proves it (ADR 0275 §5); the
note's text names both workers. Tests for a resolved issue corrected, link
and set keeping the worker current, and a take-over reason with a secret's
shape. The ready-to-verify note says an issue resolves from fixing.

modules/mesh-issues/cmd/mesh-issues/tracker.go

@@ -463,7 +463,7 @@ func (t *Tracker) move(by string, a MoveAsk) (*Moved, error) {
 			changed = append(changed, "by")
 		}
 		if work.from != "" {
-			is.Notes = append(is.Notes, Note{By: worker, At: at, Text: takeOverNote(work, worker, takeOver, prev)})
+			is.Notes = append(is.Notes, Note{By: by, At: at, Text: takeOverNote(work, worker, takeOver, prev)})
 		}
 		// The same status again only to change what it holds: a fix named while the issue stays located, to be
 		// resolved once it is delivered and proven (ADR 0281 §3).