test: make the ecosystem fault suite fail when the feature is deleted

Several assertions passed against code with the behaviour removed. The
independent-outage test shared no state to begin with, the capability
fixture used to prove read-only filtering was already mutating, and
route-level faults were simulated with a separate fake instead of the
shared one. The harness now takes per-route faults and a ticking clock,
so durations are measurable and one dead endpoint can be shown not to
mute a whole service. New cases cover a resolved reference with no
entity, a rejected credential, a malformed Praxis body, foreign items
in a scoped response, named truncation, traces staying out of facts,
and enrichment making progress while its oldest batch is backed off.

Found in review of #82.

cmd/mavend/ecosystem_harness_test.go

@@ -19,6 +19,13 @@ func praxisActDec(fn string) router.Decision {
 	return router.Decision{Intent: router.IntentAct, Slots: router.Slots{Fn: fn, HasFn: true}}
 }
 
+// praxisItemDec is praxisActDec for the lifecycle verbs, which need an item id
+// in the value slot. Without one they answer "which item?" and never reach
+// Praxis at all, which makes them useless for testing a Praxis outage.
+func praxisItemDec(fn, itemID string) router.Decision {
+	return router.Decision{Intent: router.IntentAct, Slots: router.Slots{Fn: fn, HasFn: true, Value: itemID}}
+}
+
 func newPraxisTestHandler(t *testing.T, praxis *fakeServer) *reactiveHandler {
 	t.Helper()
 	st := newTestStore(t)