[sgl-router] Add Kimi-K3 rendering with SGLang parity (#40390)

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

experimental/sgl-router/tests/fixtures/kimi_k3.rs

@@ -0,0 +1,28 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 The SGLang Authors
+// SPDX-License-Identifier: Apache-2.0
+
+use base64::{engine::general_purpose::STANDARD, Engine};
+
+pub fn tokenizer() -> tempfile::TempDir {
+    let dir = tempfile::tempdir().unwrap();
+    let bytes = (0..=255u8).map(|byte| vec![byte]);
+    let merges = include_str!("kimi_k3/merges.txt")
+        .split_whitespace()
+        .map(|s| s.as_bytes().to_vec());
+    let vocab: String = bytes
+        .chain(merges)
+        .enumerate()
+        .map(|(rank, token)| format!("{} {rank}\n", STANDARD.encode(token)))
+        .collect();
+    std::fs::write(dir.path().join("tiktoken.model"), vocab).unwrap();
+    for (name, contents) in [
+        ("config.json", r#"{"model_type":"kimi_k3"}"#),
+        (
+            "tokenizer_config.json",
+            include_str!("kimi_k3/tokenizer_config.json"),
+        ),
+    ] {
+        std::fs::write(dir.path().join(name), contents).unwrap();
+    }
+    dir
+}