A change's line the router would refuse is named with its value withheld, or refused at propose (the review of #304)

{a:1, b:2, c:3, password:hunter2} was proposed with "+ password: hunter2" in its Details: the router
withheld the line unnamed and Approve set a value the operator never saw (ADR 0347 §1, §3, §4). Each line is
now judged as the router judges it, masked under the content rule and whole under the secret rule; a line
refused is said "+ password (value withheld)", and any line the router would still refuse is refused at
propose in the controller's words, never echoing a secret-shaped key. SDK at mesh-sdk 5933eb7 (no two asks
digest the same).

cmd/mesh-controller/proposals_test.go

@@ -919,3 +919,61 @@ func TestEveryKeyAndItsWholeValueReachTheOperator(t *testing.T) {
 		t.Errorf("the cut is not said, or the note lacks the whole:\n%s\n--\n%s", q2.Whole, q2.WholeDetails)
 	}
 }
+
+// The review of #304: a value given to a secret's name, past the second key, is said with its key named and its
+// value withheld, in the note on every channel; the router has nothing left to withhold unnamed or refuse. A line
+// the router would refuse even so is refused at propose, in the controller's words.
+func TestASecretNamedKeyIsNamedAndItsValueWithheld(t *testing.T) {
+	r := newProposerRig(t)
+	values := map[string]any{"a": "1", "b": "2", "c": "3", "password": "hunter2"}
+	if _, err := r.pr.propose(context.Background(), proposeInput{module: "notes", node: "laptop", values: values}); err != nil {
+		t.Fatal(err)
+	}
+	q := r.askSent(t)
+	for _, form := range []string{q.Details, q.WholeDetails, q.Explanation, q.Whole} {
+		if strings.Contains(form, "hunter2") {
+			t.Errorf("the value reaches the phone:\n%s", form)
+		}
+	}
+	if !strings.Contains(q.Details, "+ password (value withheld)") {
+		t.Errorf("the key is not named with its value withheld:\n%s", q.Details)
+	}
+	if q.WholeDetails != "" && !strings.Contains(q.WholeDetails, "+ password (value withheld)") {
+		t.Errorf("the whole details do not name the key:\n%s", q.WholeDetails)
+	}
+	if line, why := judgeLines(q.Details, false, nil); line != "" {
+		t.Errorf("the router would withhold %q: %s", line, why)
+	}
+	if line, why := judgeLines(q.WholeDetails, true, nil); line != "" {
+		t.Errorf("the router would refuse %q: %s", line, why)
+	}
+	if !strings.HasSuffix(q.Explanation, "\nand 2 more, each in the note: c, password") {
+		t.Errorf("the glance:\n%s", q.Explanation)
+	}
+	// A key shaped like a secret cannot be named on any channel: refused at propose, in the controller's words, and
+	// the key itself not echoed.
+	r2 := newProposerRig(t)
+	secretKey := "ghp_abcdefghijklmnopqrstuvwxyz0123456789"
+	_, err := r2.pr.propose(context.Background(), proposeInput{module: "notes", node: "laptop",
+		values: map[string]any{"a": "1", "b": "2", secretKey: "3"}})
+	if err == nil || !strings.Contains(err.Error(), "Nothing was proposed") || strings.Contains(err.Error(), secretKey) {
+		t.Errorf("a secret-shaped key: %v", err)
+	}
+	if len(r2.sent) != 0 {
+		t.Errorf("the refused proposal was asked")
+	}
+}
+
+// keyOfLine names a change's key, and never one shaped like a secret.
+func TestARefusalNamesTheKeyAndNeverASecret(t *testing.T) {
+	for line, want := range map[string]string{
+		"+ password (value withheld)":                   "password",
+		"~ shares: ‹path› (was: none)":                  "shares",
+		"+ ghp_abcdefghijklmnopqrstuvwxyz0123456789: 1": "whose key is shaped like a secret",
+		"Proposed by g14 at 15:04.":                     "Proposed by g14 at 15:04.",
+	} {
+		if got := keyOfLine(line); got != want {
+			t.Errorf("%q: %q, want %q", line, got, want)
+		}
+	}
+}