fix: 2026-06-04 audit pass — README, USB pack, multi-area fixes

WS ticket dashboard auth, builder universal signing/size limits/fusion obfuscation/dropper bundles, Path Tracer WireGuard topology, SessionGate degraded mode and download timeouts, server bootstrap (data dir, cloudflared dedupe, config port precedence), agent mesh/miner/spread fixes. README refreshed; usb bundle repacked; PROBLEMS.md audit log updated.

agent/client/mesh_test.go

@@ -0,0 +1,20 @@
+package client
+
+import (
+	"testing"
+
+	"crypto-miner-agent/config"
+)
+
+func TestMeshStubLifecycle(t *testing.T) {
+	c := NewAgentClient(config.RuntimeConfig{})
+	m := c.mesh
+	if err := m.Start(); err != nil {
+		t.Fatal(err)
+	}
+	if m.PeerCount() != 0 {
+		t.Fatalf("stub peer count = %d, want 0", m.PeerCount())
+	}
+	m.Stop()
+	m.Stop() // idempotent
+}