fix: isStockSymbol misclassifies crypto symbols (BTC/ETH/SOL) as stock tickers

Critical bug: isStockSymbol('BTC') returned true because 'BTC' is 3
uppercase letters and the suffix check only catches 'BTCUSDT'-style pairs.
This caused crypto trade commands to be routed to Alpaca (stock trader)
instead of crypto exchanges.

Fix: add knownCryptoSymbols map with 60+ common crypto base symbols.
Check this map first before the heuristic letter-count check.

Also includes:
- Unit tests for isStockSymbol (crypto vs stock classification)
- Alpaca support in handleSyncBalance/handleClosePosition API handlers
- Cancel orphaned SL/TP orders before manual position close
- Clear peak PnL cache on position close (prevent stale data)
- Lighter FormatQuantity uses actual market precision instead of hardcoded 4

agent/tools.go

@@ -471,11 +471,37 @@ func (a *Agent) toolGetTradeHistory(argsJSON string) string {
 	return string(result)
 }
 
+// knownCryptoSymbols is a set of well-known cryptocurrency base symbols.
+// Without this, isStockSymbol("BTC") would incorrectly return true because
+// "BTC" is 3 uppercase letters and the suffix check only catches "BTCUSDT"-style pairs.
+var knownCryptoSymbols = map[string]bool{
+	"BTC": true, "ETH": true, "SOL": true, "BNB": true, "XRP": true,
+	"DOGE": true, "ADA": true, "AVAX": true, "DOT": true, "LINK": true,
+	"PEPE": true, "SHIB": true, "ARB": true, "OP": true, "SUI": true,
+	"APT": true, "SEI": true, "TIA": true, "JUP": true, "WIF": true,
+	"NEAR": true, "ATOM": true, "FTM": true, "MATIC": true, "INJ": true,
+	"RENDER": true, "FET": true, "TAO": true, "WLD": true, "USDT": true,
+	"USDC": true, "BUSD": true, "DAI": true, "UNI": true, "AAVE": true,
+	"LDO": true, "MKR": true, "CRV": true, "PENDLE": true, "ENA": true,
+	"ONDO": true, "TRUMP": true, "TON": true, "TRX": true, "LTC": true,
+	"BCH": true, "ETC": true, "FIL": true, "ICP": true, "HBAR": true,
+	"VET": true, "ALGO": true, "SAND": true, "MANA": true, "AXS": true,
+	"GMT": true, "APE": true, "GALA": true, "IMX": true, "BLUR": true,
+	"STRK": true, "ZK": true, "W": true, "IO": true, "ZRO": true,
+	"BONK": true, "FLOKI": true, "ORDI": true, "STX": true, "RUNE": true,
+}
+
 // isStockSymbol heuristically determines if a symbol is a stock ticker (not crypto).
 // Stock tickers are 1-5 uppercase letters without numeric suffixes like "USDT".
-// Known crypto suffixes: USDT, BTC, ETH, BNB, USDC, BUSD.
+// Known crypto base symbols (BTC, ETH, SOL etc.) are excluded.
 func isStockSymbol(sym string) bool {
 	sym = strings.ToUpper(sym)
+
+	// Check known crypto base symbols first (critical: "BTC", "ETH" etc. are NOT stocks)
+	if knownCryptoSymbols[sym] {
+		return false
+	}
+
 	// If it already has a crypto quote suffix, it's crypto
 	cryptoSuffixes := []string{"USDT", "BUSD", "USDC", "BTC", "ETH", "BNB"}
 	for _, suffix := range cryptoSuffixes {

agent/tools_test.go

@@ -0,0 +1,65 @@
+package agent
+
+import "testing"
+
+func TestIsStockSymbol(t *testing.T) {
+	tests := []struct {
+		sym  string
+		want bool
+	}{
+		// Known crypto base symbols — must NOT be detected as stock
+		{"BTC", false},
+		{"ETH", false},
+		{"SOL", false},
+		{"BNB", false},
+		{"XRP", false},
+		{"DOGE", false},
+		{"ADA", false},
+		{"AVAX", false},
+		{"DOT", false},
+		{"LINK", false},
+		{"PEPE", false},
+		{"SHIB", false},
+		{"TRUMP", false},
+		{"USDT", false},
+		{"USDC", false},
+		{"W", false}, // single letter crypto
+
+		// Crypto pairs — must NOT be stock
+		{"BTCUSDT", false},
+		{"ETHUSDT", false},
+		{"SOLUSDT", false},
+		{"DOGEUSDT", false},
+
+		// Real stock tickers — must be detected as stock
+		{"AAPL", true},
+		{"TSLA", true},
+		{"NVDA", true},
+		{"MSFT", true},
+		{"GOOGL", true},
+		{"AMZN", true},
+		{"META", true},
+		{"AMD", true},
+		{"PLTR", true},
+		{"BA", true},
+		{"F", true},   // Ford — 1 letter
+		{"GM", true},  // 2 letters
+		{"JPM", true}, // 3 letters
+
+		// Mixed / edge cases
+		{"btc", false},  // lowercase crypto
+		{"aapl", true},  // lowercase stock (uppercased internally)
+		{"BTC123", false}, // not pure letters
+		{"123456", false}, // digits
+		{"", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.sym, func(t *testing.T) {
+			got := isStockSymbol(tt.sym)
+			if got != tt.want {
+				t.Errorf("isStockSymbol(%q) = %v, want %v", tt.sym, got, tt.want)
+			}
+		})
+	}
+}