Handle stale sync state in client UI

src/web/styles.css

@@ -49,6 +49,100 @@ p {
   background: light-dark(oklch(0.965 0.006 145), oklch(0.18 0.012 145));
 }
 
+.app-boot {
+  min-height: 100vh;
+  display: grid;
+  place-content: center;
+  justify-items: start;
+  gap: 14px;
+  padding: 32px;
+  background: light-dark(oklch(0.965 0.006 145), oklch(0.18 0.012 145));
+  color: light-dark(oklch(0.24 0.014 145), oklch(0.93 0.008 145));
+  font-family: 'JetBrains Mono', 'SF Mono', ui-monospace, Menlo, monospace;
+}
+
+.app-boot > span,
+.app-boot summary {
+  color: light-dark(oklch(0.53 0.014 145), oklch(0.68 0.012 145));
+  font-size: 11px;
+}
+
+.app-boot h1 {
+  max-width: 22ch;
+  margin: 0;
+  font-size: clamp(22px, 5vw, 34px);
+  letter-spacing: -0.05em;
+}
+
+.app-boot p {
+  max-width: 58ch;
+  color: light-dark(oklch(0.53 0.014 145), oklch(0.68 0.012 145));
+  font-size: 12px;
+  line-height: 1.7;
+}
+
+.app-boot button,
+.client-stale-banner button {
+  padding: 8px 12px;
+  border: 0;
+  border-radius: 8px;
+  background: light-dark(oklch(0.91 0.02 185), oklch(0.28 0.03 185));
+  cursor: pointer;
+}
+
+.app-boot button:focus-visible,
+.client-stale-banner button:focus-visible {
+  outline: 2px solid oklch(0.65 0.11 185);
+  outline-offset: 3px;
+}
+
+.app-boot details {
+  max-width: min(640px, calc(100vw - 64px));
+  margin-top: 8px;
+}
+
+.app-boot summary {
+  cursor: pointer;
+}
+
+.app-boot code,
+.app-boot pre {
+  display: block;
+  overflow-x: auto;
+  margin: 12px 0 0;
+  font-size: 11px;
+  line-height: 1.6;
+  white-space: pre-wrap;
+}
+
+.client-stale-banner {
+  position: fixed;
+  top: 16px;
+  left: 50%;
+  z-index: 60;
+  display: grid;
+  grid-template-columns: auto auto auto;
+  align-items: center;
+  gap: 12px;
+  padding: 9px 10px 9px 14px;
+  border-radius: 12px;
+  background: color-mix(in oklch, var(--client-panel) 90%, transparent);
+  box-shadow: 0 10px 32px oklch(0.08 0.015 145 / 0.14);
+  backdrop-filter: blur(12px);
+  color: var(--client-muted);
+  font: 600 10px/1.3 'JetBrains Mono', 'SF Mono', ui-monospace, Menlo, monospace;
+  transform: translateX(-50%);
+}
+
+.client-stale-banner strong {
+  color: var(--client-text);
+}
+
+.client-stale-banner button {
+  color: var(--client-text);
+  font-size: 10px;
+}
+
 /* ============ Client overview ============ */
 
 .app.client-app {
@@ -1897,6 +1991,16 @@ p {
     padding: 20px 14px;
   }
 
+  .client-stale-banner {
+    width: calc(100% - 28px);
+    grid-template-columns: 1fr auto;
+  }
+
+  .client-stale-banner span {
+    grid-column: 1 / -1;
+    grid-row: 2;
+  }
+
   .client-panel {
     position: static;
     grid-template-columns: 1fr;