fix: chart visibility, heartbeat grace period, form alignment, agents page crash

- ReputationChart: larger filled dots (r=4), solid fill for better
  dark-mode visibility
- heartbeat_miss: skip agents registered less than 5 minutes ago
  (registered_at < cutoff) so new agents aren't immediately penalized
- ClaimTokenSection: match button height to input field (h-[38px])
- ProviderAgentsPage: null-safe access on total_calls, success_rate,
  avg_latency_ms to prevent crash

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

Author: gcmsg

internal/reputation/postgres.go

@@ -163,9 +163,10 @@ func (s *PostgresStore) UnsetAgentVerified(ctx context.Context, agentID string)
 // ListStaleOnlineAgents returns IDs of agents whose status is online but
 // whose last heartbeat is older than the given timeout.
 func (s *PostgresStore) ListStaleOnlineAgents(ctx context.Context, timeout time.Duration) ([]string, error) {
+	cutoff := time.Now().UTC().Add(-timeout)
 	rows, err := s.db.QueryContext(ctx,
-		`SELECT id FROM agents WHERE status = 'online' AND last_heartbeat < $1`,
-		time.Now().UTC().Add(-timeout),
+		`SELECT id FROM agents WHERE status = 'online' AND last_heartbeat < $1 AND registered_at < $1`,
+		cutoff,
 	)
 	if err != nil {
 		return nil, err

internal/reputation/sqlite.go

@@ -177,9 +177,10 @@ func (s *SQLiteStore) UnsetAgentVerified(ctx context.Context, agentID string) er
 // ListStaleOnlineAgents returns IDs of agents whose status is online but
 // whose last heartbeat is older than the given timeout.
 func (s *SQLiteStore) ListStaleOnlineAgents(ctx context.Context, timeout time.Duration) ([]string, error) {
+	cutoff := time.Now().UTC().Add(-timeout).Format(time.RFC3339)
 	rows, err := s.db.QueryContext(ctx,
-		`SELECT id FROM agents WHERE status = 'online' AND last_heartbeat < ?`,
-		time.Now().UTC().Add(-timeout).Format(time.RFC3339),
+		`SELECT id FROM agents WHERE status = 'online' AND last_heartbeat < ? AND registered_at < ?`,
+		cutoff, cutoff,
 	)
 	if err != nil {
 		return nil, err

web/app/src/components/provider/ClaimTokenSection.tsx

@@ -187,10 +187,9 @@ Full documentation: https://github.com/peerclaw/peerclaw/blob/main/docs/GUIDE.md
             />
           </div>
           <Button
-            size="sm"
             onClick={handleGenerate}
             disabled={generating}
-            className="shrink-0"
+            className="shrink-0 h-[38px]"
           >
             {generating ? (
               <Loader2 className="size-4 animate-spin" />

web/app/src/components/public/ReputationChart.tsx

@@ -62,8 +62,9 @@ export function ReputationChart({ events }: { events: ReputationEvent[] }) {
           dataKey="score"
           stroke="hsl(var(--chart-1))"
           strokeWidth={2}
-          dot={{ r: 3 }}
-          activeDot={{ r: 5 }}
+          dot={{ r: 4, fill: "hsl(var(--chart-1))", strokeWidth: 0 }}
+          activeDot={{ r: 6, fill: "hsl(var(--chart-1))", strokeWidth: 2, stroke: "hsl(var(--card))" }}
+          connectNulls
         />
       </LineChart>
     </ResponsiveContainer>

web/app/src/pages/ProviderAgentsPage.tsx

@@ -105,13 +105,13 @@ export function ProviderAgentsPage() {
                   </Badge>
                 </TableCell>
                 <TableCell className="text-muted-foreground">
-                  {agent.total_calls.toLocaleString()}
+                  {(agent.total_calls ?? 0).toLocaleString()}
                 </TableCell>
                 <TableCell className="text-muted-foreground">
-                  {agent.success_rate.toFixed(1)}%
+                  {(agent.success_rate ?? 0).toFixed(1)}%
                 </TableCell>
                 <TableCell className="text-muted-foreground">
-                  {agent.avg_latency_ms.toFixed(0)}ms
+                  {(agent.avg_latency_ms ?? 0).toFixed(0)}ms
                 </TableCell>
               </TableRow>
             ))}