fix(sub): bound what a remote routing profile renders to

Remote routing sources are fetched documents the panel re-renders on
every subscription request. A Clash YAML document stays small through
aliases, which decode to one shared value but are written out in full,
so it now has to fit a 4 MiB written-size budget and 16 levels of
nesting when it is accepted (and when a persisted copy is loaded). A JSON
routing profile could repeat route groups, each copy repeating every
site list; a group now counts once, since a repeat can never match.

internal/sub/remote_routing_test.go

@@ -3,6 +3,7 @@ package sub
 import (
 	"encoding/base64"
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -748,3 +749,32 @@ rules:
 		t.Fatalf("requests=%d, want 1", requests.Load())
 	}
 }
+
+// Aliases decode to one shared value but the encoder writes every copy out, on each Clash
+// request, so a small remote document must not be accepted if it marshals out of bounds.
+func TestNormalizeClashRoutingRefusesWhatMarshalsOutOfBounds(t *testing.T) {
+	var laughs strings.Builder
+	laughs.WriteString("a0: &a0 [\"" + strings.Repeat("x", 64) + "\"]\n")
+	for i := 1; i <= 9; i++ {
+		fmt.Fprintf(&laughs, "a%d: &a%d [", i, i)
+		for j := range 10 {
+			if j > 0 {
+				laughs.WriteString(",")
+			}
+			fmt.Fprintf(&laughs, "*a%d", i-1)
+		}
+		laughs.WriteString("]\n")
+	}
+	bomb := laughs.String() + "rule-providers:\n  p: {type: inline, behavior: domain, payload: *a9}\nrules:\n  - RULE-SET,p,DIRECT\n  - MATCH,DIRECT\n"
+	if _, _, err := normalizeClashRouting([]byte(bomb)); err == nil || !strings.Contains(err.Error(), "too large") {
+		t.Fatalf("alias bomb = %v, want it refused as too large", err)
+	}
+	deep := "rules:\n  - MATCH,DIRECT\nrule-providers:\n  p: {type: inline, behavior: domain, payload: " + strings.Repeat("[", 40) + strings.Repeat("]", 40) + "}\n"
+	if _, _, err := normalizeClashRouting([]byte(deep)); err == nil {
+		t.Fatal("a document nested 40 levels deep was accepted")
+	}
+	anchored := "x: &common {type: http, behavior: domain, interval: 86400}\nrule-providers:\n  ads: {<<: *common, url: \"https://example.com/ads.yaml\"}\nrules:\n  - RULE-SET,ads,REJECT\n  - MATCH,DIRECT\n"
+	if _, _, err := normalizeClashRouting([]byte(anchored)); err != nil {
+		t.Fatalf("an ordinary anchored document was refused: %v", err)
+	}
+}