feat(ui): add ScopeTrail component for scope-based breadcrumbs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/components/ScopeTrail.module.css

@@ -0,0 +1,40 @@
+.trail {
+  display: flex;
+  align-items: center;
+  gap: 0;
+  font-size: 0.8125rem;
+  color: var(--text-muted);
+  min-height: 1.5rem;
+}
+
+.segment {
+  display: inline-flex;
+  align-items: center;
+}
+
+.link {
+  color: var(--text-secondary);
+  text-decoration: none;
+  cursor: pointer;
+  background: none;
+  border: none;
+  padding: 0;
+  font: inherit;
+  font-size: 0.8125rem;
+}
+
+.link:hover {
+  color: var(--amber);
+  text-decoration: underline;
+}
+
+.separator {
+  margin: 0 0.375rem;
+  color: var(--text-muted);
+  user-select: none;
+}
+
+.current {
+  color: var(--text-primary);
+  font-weight: 500;
+}

ui/src/components/ScopeTrail.tsx

@@ -0,0 +1,38 @@
+import type { Scope } from '../hooks/useScope';
+import styles from './ScopeTrail.module.css';
+
+interface ScopeTrailProps {
+  scope: Scope;
+  onNavigate: (path: string) => void;
+}
+
+export function ScopeTrail({ scope, onNavigate }: ScopeTrailProps) {
+  const segments: { label: string; path: string }[] = [
+    { label: 'All Applications', path: `/${scope.tab}` },
+  ];
+
+  if (scope.appId) {
+    segments.push({ label: scope.appId, path: `/${scope.tab}/${scope.appId}` });
+  }
+
+  if (scope.routeId) {
+    segments.push({ label: scope.routeId, path: `/${scope.tab}/${scope.appId}/${scope.routeId}` });
+  }
+
+  return (
+    <nav className={styles.trail}>
+      {segments.map((seg, i) => (
+        <span key={seg.path} className={styles.segment}>
+          {i > 0 && <span className={styles.separator}>&gt;</span>}
+          {i < segments.length - 1 ? (
+            <button className={styles.link} onClick={() => onNavigate(seg.path)}>
+              {seg.label}
+            </button>
+          ) : (
+            <span className={styles.current}>{seg.label}</span>
+          )}
+        </span>
+      ))}
+    </nav>
+  );
+}