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/personalboundary_test.go

@@ -70,7 +70,7 @@ func TestONNXPersonalBoundary(t *testing.T) {
 		{"how do i boil an egg", false},
 	}
 
-	h := &reactiveHandler{embedder: emb}
+	h := &reactiveHandler{recall: recallWiring{embedder: emb}}
 	ctx := context.Background()
 	wrong := 0
 	for _, c := range cases {
@@ -80,7 +80,7 @@ func TestONNXPersonalBoundary(t *testing.T) {
 		}
 		turn := &queryTurn{dec: router.Decision{Utterance: c.utterance}, vec: vec}
 		got := h.isPersonalTurn(ctx, turn)
-		p, w, ok := h.boundary.score(vec)
+		p, w, ok := h.recall.boundary.score(vec)
 		if !ok {
 			t.Fatal("seeds did not load with a working embedder")
 		}