mavend: record which channel a quiet toggle arrived on

resolveQuietToggle runs inside runTurn, so mavweb /api/chat and telegram reach
it as well as the microphone. Every toggle was written with Source "tap:voice"
regardless, which left the facts table claiming a mic flipped a setting nobody
spoke to. This is the one function whose own doc comment calls it a
network-reachable way to change a daemon-wide setting, and provenance is the
first column read when asking why quiet mode is on.

runTurn now takes the channel it was entered from and the toggle writes it:
"tap:voice" from HandlePushToTalk, "tap:text" from handleText.

Found in review of #53.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TrVSBKe3RFDF4fGYKWYQnX

cmd/mavend/simulator_test.go

@@ -466,7 +466,7 @@ func (w *simWorld) stimulate(ctx context.Context, s step) {
 
 	switch {
 	case s.Say != "":
-		reply := w.handler.runTurn(ctx, s.Say)
+		reply := w.handler.runTurn(ctx, s.Say, sourceText)
 		w.replies = append(w.replies, reply)
 		w.logf("он: %s", s.Say)
 		w.logf("она: %s", reply)