feat(agent): surface the AI500 index board in chat, tools, and sidebar

- provider/nofxos: GetAI500ListCached — 5min TTL cache with stale
  fallback on upstream failure; ResolveClient routes through the claw402
  gateway when a wallet key is configured (user's claw402 model key ->
  CLAW402_WALLET_KEY env -> direct nofxos)
- new GET /api/ai500 endpoint serving the score-sorted board
- new get_ai500_list agent tool + prompt rule: when the user wants coin
  picks or creates a strategy without naming coins, consult AI500's
  high-scoring entries by default
- web: AI500 sidebar panel (rank, score badge, gain since entry,
  5min auto-refresh); clicking an entry asks the agent to analyze it

provider/nofxos/client_resolve.go

@@ -0,0 +1,32 @@
+package nofxos
+
+import (
+	"os"
+	"strings"
+
+	"nofx/logger"
+)
+
+// ResolveClient returns a nofxos data client, routed through the claw402
+// x402 payment gateway when a wallet key is available. Resolution order:
+// the explicit walletKey argument, then the CLAW402_WALLET_KEY environment
+// variable, then the direct nofxos.ai client with the default auth key.
+func ResolveClient(walletKey string) *Client {
+	walletKey = strings.TrimSpace(walletKey)
+	if walletKey == "" {
+		walletKey = strings.TrimSpace(os.Getenv("CLAW402_WALLET_KEY"))
+	}
+	client := NewClient(DefaultBaseURL, DefaultAuthKey)
+	if walletKey == "" {
+		return client
+	}
+
+	claw402URL := strings.TrimSpace(os.Getenv("CLAW402_URL"))
+	claw402Client, err := NewClaw402DataClient(claw402URL, walletKey, &logger.MCPLogger{})
+	if err != nil {
+		logger.Warnf("⚠️ Failed to init claw402 data client: %v (using direct nofxos.ai)", err)
+		return client
+	}
+	client.SetClaw402(claw402Client)
+	return client
+}