mavend: group the recall fields into one wiring struct (V-433)

The review comment asked for basic DI. The answer is the idiom voice.go
already had for capabilities — a cohesive *Wiring struct — applied to a
group that is not a capability toggle, plus the decision written down so
it is a rule and not a habit.

recallWiring holds the embedder, the vector store, the personal boundary
and the two numbers that gate an answer. They sat in three places on
reactiveHandler, with the gate numbers a hundred lines from the store
they gate. Its zero value means no recall, so it is a value, not a
pointer like the optional-capability groups.

dataStore stays out of it. patterns.go, ecosystem_acts.go and confirm.go
use it, so it is not part of this cluster.

docs/handler-wiring.md records the choice, rejects a container or a
wire-style generator outright, defers narrow per-handler interfaces to
the package split that would justify them, and states the constraint the
task named: a wiring change does not ride a feature PR.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/mavend/feeds_test.go

@@ -29,12 +29,12 @@ func buildFeedHandler(t *testing.T, feedsOn bool, notes ...ipc.Note) *reactiveHa
 		}
 	}
 	return &reactiveHandler{
-		api:      ipc.NewStoreAPI(st),
-		replier:  voice.NewStubReplier(),
-		phraser:  phraser.NewStub(),
-		now:      func() time.Time { return now },
-		feedsOn:  feedsOn,
-		embedder: nil,
+		api:     ipc.NewStoreAPI(st),
+		replier: voice.NewStubReplier(),
+		phraser: phraser.NewStub(),
+		now:     func() time.Time { return now },
+		feedsOn: feedsOn,
+		recall:  recallWiring{embedder: nil},
 	}
 }