mesh-issues: an issue says who works on it, and resolves only from fixing (hq issue 399)

Two agents could start on one issue without seeing each other, and an issue
could be resolved without anyone having said they started its fix. A move to
diagnosing or fixing now names by, the worker as who@node; get and list show
the worker with since and stale; another worker is refused while it is
current unless take-over says why (noted); a worker untouched for
worker-stale-after (24h) may be taken over from without a reason. Resolved is
reached only from fixing. The moved event carries by, since and caller.
Fixing counts as not closed for the triage and the duplicate check.
hq ADR 0283.

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

@@ -88,6 +88,7 @@ func (t *Tracker) set(by string, a SetAsk, onlyEmpty bool) (*SetDone, error) {
 		if len(changed) == 0 {
 			return errNothing
 		}
+		touch(is, by, t.now())
 		return nil
 	})
 	if errors.Is(err, errNothing) {
@@ -270,6 +271,8 @@ type View struct {
 	Ready    bool     `json:"ready"`
 	// Delivery is whether its fix is delivered, in words (ADR 0281).
 	Delivery string `json:"delivery,omitempty"`
+	// WorkerStale says nothing was done on it by its worker, or anyone, for worker-stale-after (ADR 0283 §2).
+	WorkerStale bool `json:"worker-stale,omitempty"`
 }
 
 // View is `get`.
@@ -283,7 +286,7 @@ func (t *Tracker) View(n uint64) (*View, error) {
 		return nil, fmt.Errorf("there is no issue %d: %w", n, ErrNoIssue)
 	}
 	return &View{Issue: is, NeededBy: neededBy(all, n), WaitsFor: waitsFor(all, is), Ready: isReady(all, is),
-		Delivery: DeliveryLine(is)}, nil
+		Delivery: DeliveryLine(is), WorkerStale: is.Worker != nil && is.Worker.stale(t.now(), t.workerStaleAfter())}, nil
 }
 
 // letGo says, for an issue that may have just let others go (its fix delivered, or wontfix), every issue it