v0.317.0: a second copy counts only on a proven different disk; the no-drive install speaks in words (felhom.eu architecture/16, build A)

Tier-2 and the one-copy notice ask the host agent (POST /disks/same-disk, agent 0.157.0): different +
proven -> made and counted; same disk -> not made (D1); unknown (VM, hidden USB serial) -> made, not
counted, the row says why (D2); a NAS never counts and no longer hides the notice (R-1075). An older
agent keeps the st_dev rule, logged once. D4: a data-folder or media app on a box with no drive is
refused in words with a link to the drives page (R-1068's raw-error half). MinAgent 0.157.0.

Claude-Session: https://claude.ai/code/session_012qRErfCoiTkvDK9N5XHbzb

controller/internal/backup/f6_single_copy_test.go

@@ -43,7 +43,7 @@ func TestRunAllTier2_IncludesVolumeOnlyApps(t *testing.T) {
 func TestSingleCopyWarning_HonestOnSingleDrive(t *testing.T) {
 	// Single-drive: only the system drive, no schedulable off-drive paths.
 	m1, _ := newTestManager(t, "/srv/sys")
-	if got := m1.singleCopyWarning(); got != singleCopyNotice {
+	if got := m1.singleCopyWarning(); got != m1.note("note.backup.single_copy") {
 		t.Errorf("single-drive box must surface the honest notice, got %q", got)
 	}