fix: refusing a From address the wallet does not hold moves nothing (closes #609)

Sign & Send wrote its refusal of a From address the selected wallet does not
hold onto the password error line, which reserves one line. The sentence runs
to about three, so it pushed Sign & Send down.

The refusal now has its own box above the password field, its sentence fixed
in index.html, holding its space from the first paint and only made visible,
as #583 did for the other
refusals. Drawing the screen and each press hide it again. A Chrome test
writes the other wallet into the stored selection, reopens the popup onto the
screen, presses Sign & Send and checks that nothing was broadcast and nothing
moved.

Model: opus-5-5

src/popup/index.html

@@ -697,9 +697,10 @@
                     id="confirm-fee-unknown-error"
                     class="mb-2 border border-border border-dashed p-2 text-xs invisible"
                 ></div>
-                <!-- Shown when Sign & Send refuses a send for its network, or
-                for its gas limit or fee. Each holds its space from the first
-                paint, so the refusal moves nothing. -->
+                <!-- Shown when Sign & Send refuses a send for its network, for
+                a From address the selected wallet does not hold, or for its
+                gas limit or fee. Each holds its space from the first paint, so
+                the refusal moves nothing. -->
                 <div
                     id="confirm-network-changed-error"
                     class="mb-2 border border-border border-dashed p-2 text-xs invisible"
@@ -708,6 +709,13 @@
                     reviewed, so it was not sent. Please go back and review it
                     again.
                 </div>
+                <div
+                    id="confirm-from-address-error"
+                    class="mb-2 border border-border border-dashed p-2 text-xs invisible"
+                >
+                    The selected wallet does not hold the From address above, so
+                    nothing was sent. Please go back and send again.
+                </div>
                 <div
                     id="confirm-fee-bound-error"
                     class="mb-2 border border-border border-dashed p-2 text-xs invisible"