Release 3.8.1.1: lighter idle UI poll, core cache, multicore ping.

Reduce idle CPU (cheap PollUI, binary cache, logbuf cap, DOM fingerprint),
speed ping/AWG HostPort, CopyBuffer pool; ship arm64 build and update notes.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/corebin/cache_test.go

@@ -0,0 +1,45 @@
+package corebin
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestResolveCacheAndStale(t *testing.T) {
+	Invalidate()
+	dir := t.TempDir()
+	path := filepath.Join(dir, "core")
+	if err := os.WriteFile(path, []byte("x"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	key := CacheKey(dir, "naive")
+	calls := 0
+	fn := func() (string, error) {
+		calls++
+		return path, nil
+	}
+	if p, err := Resolve(key, fn); err != nil || p != path || calls != 1 {
+		t.Fatalf("first: path=%q calls=%d err=%v", p, calls, err)
+	}
+	if p, err := Resolve(key, fn); err != nil || p != path || calls != 1 {
+		t.Fatalf("cached: path=%q calls=%d err=%v", p, calls, err)
+	}
+	_ = os.Remove(path)
+	if _, err := Resolve(key, fn); err != nil {
+		// fn returns removed path; Resolve still succeeds but next Stat misses
+		t.Fatalf("unexpected err after delete before recreate: %v", err)
+	}
+	if calls != 2 {
+		t.Fatalf("expected refresh call, got %d", calls)
+	}
+	if err := os.WriteFile(path, []byte("y"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if p, err := Resolve(key, fn); err != nil || p != path {
+		t.Fatalf("after recreate: %q %v", p, err)
+	}
+	if ProtoKey("vless") != "xray" || ProtoKey("naive") != "naive" {
+		t.Fatal("ProtoKey")
+	}
+}