feat: server-side launch preflight with structured checks and runtime AI wallet health

- POST /api/launch/preflight and GET /api/traders/:id/preflight run every
  launch prerequisite (AI model credential, claw402 wallet key + Base USDC
  balance, strategy, exchange config, live account state, funding minimums)
  and return a structured checklist with stable codes; minimums (1 USDC AI
  fee / 12 USDC trading) now live server-side and are exposed in the response.
- POST /traders/:id/start enforces the preflight (400 with error_key
  trader.start.preflight_failed + full checklist; ?force=true to override).
  Funding gates use max(available, equity) so restarting a bot with deployed
  margin is not blocked; indeterminate probes (RPC outage) degrade to
  warnings instead of blocking.
- Run loop now surfaces runtime health via GetStatus: safe_mode(+reason) and
  ai_wallet_status/balance (ok|low|empty|unknown), including typed detection
  of claw402 ErrInsufficientFunds instead of burying it in logs; safe-mode
  state is mutex-guarded for API readers.
- Onboarding wallet endpoints switch to the cached, error-aware balance query
  and report balance_status so the UI can tell an RPC outage from an empty
  wallet.

trader/runtime_health.go

@@ -0,0 +1,82 @@
+package trader
+
+import (
+	"time"
+)
+
+// Runtime health state written by the run-loop goroutine and read by the API
+// layer (GetStatus). Everything here goes through runtimeHealthMu so the
+// dashboard can poll without racing the trading loop.
+
+// AI fee wallet health statuses exposed via GetStatus as "ai_wallet_status".
+const (
+	AIWalletStatusOK      = "ok"
+	AIWalletStatusLow     = "low"
+	AIWalletStatusEmpty   = "empty"
+	AIWalletStatusUnknown = "unknown"
+)
+
+// aiWalletLowThresholdUSDC mirrors api.MinAIFeeUSDC: below this the wallet
+// cannot reliably pay for the next AI/data calls.
+const aiWalletLowThresholdUSDC = 1.0
+
+func (at *AutoTrader) setSafeMode(active bool, reason string) {
+	at.runtimeHealthMu.Lock()
+	at.safeMode = active
+	at.safeModeReason = reason
+	at.runtimeHealthMu.Unlock()
+}
+
+func (at *AutoTrader) isSafeMode() bool {
+	at.runtimeHealthMu.RLock()
+	defer at.runtimeHealthMu.RUnlock()
+	return at.safeMode
+}
+
+func (at *AutoTrader) safeModeState() (bool, string) {
+	at.runtimeHealthMu.RLock()
+	defer at.runtimeHealthMu.RUnlock()
+	return at.safeMode, at.safeModeReason
+}
+
+// setAIWalletHealth records a fresh balance observation for the claw402 wallet.
+func (at *AutoTrader) setAIWalletHealth(balance float64) {
+	status := AIWalletStatusOK
+	switch {
+	case balance <= 0:
+		status = AIWalletStatusEmpty
+	case balance < aiWalletLowThresholdUSDC:
+		status = AIWalletStatusLow
+	}
+
+	at.runtimeHealthMu.Lock()
+	at.aiWalletStatus = status
+	at.aiWalletBalanceUSDC = balance
+	at.aiWalletCheckedAt = time.Now().UTC()
+	at.runtimeHealthMu.Unlock()
+}
+
+// markAIWalletHealthUnknown keeps the last observed balance but flags that the
+// current reading could not be refreshed (e.g. Base RPC unreachable).
+func (at *AutoTrader) markAIWalletHealthUnknown() {
+	at.runtimeHealthMu.Lock()
+	at.aiWalletStatus = AIWalletStatusUnknown
+	at.aiWalletCheckedAt = time.Now().UTC()
+	at.runtimeHealthMu.Unlock()
+}
+
+// markAIWalletEmptyFromPayment records a payment-layer rejection: the wallet
+// definitively could not cover an AI call.
+func (at *AutoTrader) markAIWalletEmptyFromPayment(balance float64) {
+	at.runtimeHealthMu.Lock()
+	at.aiWalletStatus = AIWalletStatusEmpty
+	at.aiWalletBalanceUSDC = balance
+	at.aiWalletCheckedAt = time.Now().UTC()
+	at.runtimeHealthMu.Unlock()
+}
+
+func (at *AutoTrader) aiWalletHealth() (status string, balance float64, checkedAt time.Time) {
+	at.runtimeHealthMu.RLock()
+	defer at.runtimeHealthMu.RUnlock()
+	return at.aiWalletStatus, at.aiWalletBalanceUSDC, at.aiWalletCheckedAt
+}