fix: context propagation in LLM calls, SSE error handling, security hardening

- Propagate request context through MCP client (Request.Ctx field)
  — Client disconnects now cancel in-flight LLM API calls (both streaming and non-streaming)
  — Prevents wasted LLM tokens when user navigates away mid-response
- proxyBinance: use http.NewRequestWithContext for context-aware upstream calls
  — Client disconnects cancel Binance proxy requests
  — Distinguishes client cancellation from upstream failures
- Fix SSE parse bug in AgentChatPage: catch block was swallowing error events
  — throw new Error(data) for 'error' events was caught by the same try/catch
  — Now parse JSON separately, then handle events outside try/catch
- Add io.LimitReader to Hyperliquid coins.go JSON decoder (4MB limit)
- Use safe.ReadAllLimited in batch ticker handler for consistency
- Sanitize URL validation error in handler_ai_model.go (was leaking raw error)
- Cache agent tool definitions (built once, reused per message)
- Sort trade history by exit time for consistent ordering

agent/tools.go

@@ -4,14 +4,20 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"sort"
 	"strings"
 	"time"
 
 	"nofx/mcp"
 )
 
-// agentTools defines the tools available to the LLM for autonomous action.
-func agentTools() []mcp.Tool {
+// cachedTools holds the static tool definitions (built once, reused per message).
+var cachedTools = buildAgentTools()
+
+// agentTools returns the tools available to the LLM for autonomous action.
+func agentTools() []mcp.Tool { return cachedTools }
+
+func buildAgentTools() []mcp.Tool {
 	return []mcp.Tool{
 		{
 			Type: "function",
@@ -423,6 +429,13 @@ func (a *Agent) toolGetTradeHistory(argsJSON string) string {
 		return `{"trades": [], "message": "no closed trades found"}`
 	}
 
+	// Sort trades by exit time (most recent first) for consistent ordering across traders
+	sort.Slice(trades, func(i, j int) bool {
+		ti, _ := trades[i]["exit_time"].(string)
+		tj, _ := trades[j]["exit_time"].(string)
+		return ti > tj // reverse chronological
+	})
+
 	// Only return up to the limit
 	if len(trades) > args.Limit {
 		trades = trades[:args.Limit]