split: refuse a model whose routed experts it has no kernel for at once, in one plain line

Before this, a start with such a file (UD-Q6_K_XL) read 55 GB of embeddings and spent more than 25 minutes loading before it gave up, so the
server's fallback to the normal layer split came very late. The check runs when the file is opened, before anything is read or placed.

src/split/src/model.cpp

@@ -1182,6 +1182,20 @@ Mtp::Mtp(const Model& m, const std::string& dir, const std::string& vocab_file)
 
 Mtp::~Mtp() { free_mtp_cards(cards); }
 
+// A file whose routed experts the engine has no kernel for is refused here, in one plain line, before anything is read into RAM or placed on
+// the cards (the app's rule, strata_control/split_engine.py, refuses it earlier; this is the same check for a start that skipped the rule). The
+// server then starts the normal layer split. Q2_0 is not listed: the Gguf has already repacked it to Q4_0.
+static void check_supported(const Gguf& g) {
+    const uint32_t ok[] = {T_Q4_K, T_Q5_K, T_Q5_1, T_Q8_0, T_Q4_0, T_IQ4_NL, T_IQ4_XS, T_IQ3_S, T_IQ3_XXS, T_IQ2_S};
+    for (const auto& kv : g.tensors()) {
+        const std::string& n = kv.first;
+        if (n.find("_exps.weight") == std::string::npos || n.find("shexp") != std::string::npos) continue;
+        if (std::find(std::begin(ok), std::end(ok), kv.second.type) == std::end(ok))
+            throw std::runtime_error("the all-cards split engine does not read this model's routed experts (" + n + " is ggml type " +
+                                     std::to_string(kv.second.type) + "); use the normal layer split");
+    }
+}
+
 Model::Model(const std::string& path, Load how, Store* store, const std::string* image) : g(path) {
     // the cards first: reading the embeddings into RAM below takes seconds on a cold cache
     {
@@ -1195,6 +1209,7 @@ Model::Model(const std::string& path, Load how, Store* store, const std::string*
                                      " of them, or build for " + std::to_string(ndev) + " (make FNX_NCARD=" + std::to_string(ndev) + ")");
         check_cards();
     }
+    check_supported(g);
 #if FNX_27B
     const std::string p = "qwen35.";
     // block_count holds the draft (nextn) layer too