chore: replace Unicode/emoji icons with Lucide React

Adds lucide-react and replaces all HTML entity and emoji icons across
the UI with proper SVG icon components. Tree-shaken — only imported
icons are bundled.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/AgentInstance/AgentInstance.tsx

@@ -1,5 +1,6 @@
 import { useMemo, useState } from 'react';
 import { useParams, Link } from 'react-router';
+import { RefreshCw, ChevronRight } from 'lucide-react';
 import {
   StatCard, StatusDot, Badge, LineChart, AreaChart, BarChart,
   EventFeed, Spinner, EmptyState, SectionHeader, MonoText,
@@ -230,11 +231,11 @@ export default function AgentInstance() {
             <Link to="/agents" className={styles.scopeLink}>
               All Agents
             </Link>
-            <span className={styles.scopeSep}>&#9656;</span>
+            <span className={styles.scopeSep}><ChevronRight size={12} /></span>
             <Link to={`/agents/${appId}`} className={styles.scopeLink}>
               {appId}
             </Link>
-            <span className={styles.scopeSep}>&#9656;</span>
+            <span className={styles.scopeSep}><ChevronRight size={12} /></span>
             <span className={styles.scopeCurrent}>{agent.name}</span>
             <StatusDot variant={statusVariant} />
             <Badge label={agent.status} color={statusColor} />
@@ -407,7 +408,7 @@ export default function AgentInstance() {
                 {logSortAsc ? '\u2191' : '\u2193'}
               </button>
               <button className={styles.refreshBtn} onClick={() => setLogRefreshTo(new Date().toISOString())} title="Refresh">
-                &#x21bb;
+                <RefreshCw size={14} />
               </button>
             </div>
           </div>
@@ -457,7 +458,7 @@ export default function AgentInstance() {
                 {eventSortAsc ? '\u2191' : '\u2193'}
               </button>
               <button className={styles.refreshBtn} onClick={() => setEventRefreshTo(new Date().toISOString())} title="Refresh">
-                &#x21bb;
+                <RefreshCw size={14} />
               </button>
             </div>
           </div>