fix(#434,#377): three post-merge CI failures, all real gaps in both ports

None of these are merge artifacts — each would have failed on either branch
alone. The merge is simply the first time all of CI ran against them: the
fireredtts3 branch's own Piper/Windows run died at the BUILD step and never
reached these, and the supertonic branch predates them.

1. LINK FAILURE under GGML_BACKEND_DL (CI job linux-backend-dl, "Build (the
   link is the test)"):

     libcrispasr.so: undefined reference to `ggml_backend_is_cpu'
     libcrispasr.so: undefined reference to `ggml_backend_cpu_set_n_threads'

   Under DL the CPU backend is a dlopen'd module, so those symbols are not
   linkable. src/core/ggml_cpu_backend.h exists precisely for this and both
   files already INCLUDED it and used core_cpu_backend::is_cpu in most places —
   the set_n_threads calls were raw, plus two raw is_cpu calls in fireredtts3.
   Swept the whole tree afterwards: every other match in src/*.cpp is a comment
   or a log string, so these two were the only real offenders.

2. UNIT TEST tests/test-arch-backend-map.cpp:265 — "every emitted backend name
   is a name a surface can open", 5 assertions. Both ports added entries to
   src/core/arch_backend_map.h and neither added the backend to the test's
   hand-maintained `known` list, so the map emitted supertonic / supertonic-tts
   / supertonic_tts / fireredtts3 / fireredtts3-redae as names no surface
   claimed to open. Added "supertonic" and "fireredtts3".

3. CLANG-FORMAT violation at src/crispasr_c_api.cpp:9673, from the auto-merged
   supertonic session arm. Reformatted and re-verified clean with the same
   clang-format-18 CI uses.

Also confirmed NOT ours, and left alone: "Piper Windows Live / Prove HTTP WAV
and chunked PCM" fails on `$asr -notmatch 'great job'`, having transcribed
"Hello how are you today?  UT-Tay Quit Job Today." The first sentence is
recovered correctly and NO commit since that workflow's last green run
(3ac0fef, 2026-09-07) touches piper, the server, or sentence chunking — checked
by path, not assumed. The gate is a single-phrase whisper-base match on TTS
audio, which is a fragile predicate. Reported rather than chased.

Author: crispasr integration

src/crispasr_c_api.cpp

@@ -9670,8 +9670,8 @@ static float* crispasr_session_synthesize_raw_impl(crispasr_session* s, const ch
     if (s->supertonic_ctx) {
         // Supertonic-3 outputs 44.1 kHz mono. Language follows the sticky
         // session languages (target first — this is the OUTPUT language).
-        const std::string lang = !s->target_language.empty() ? s->target_language
-                                 : (!s->source_language.empty() ? s->source_language : "");
+        const std::string lang =
+            !s->target_language.empty() ? s->target_language : (!s->source_language.empty() ? s->source_language : "");
         if (!lang.empty() && lang != "auto")
             supertonic_set_language(s->supertonic_ctx, lang.c_str());
         int n = 0;

src/fireredtts3_tts.cpp

@@ -1200,10 +1200,10 @@ extern "C" struct fireredtts3_tts_context* fireredtts3_tts_init_from_file(
     if (!ctx->backend)
         ctx->backend = core_cpu_backend::init();
     ctx->backend_cpu = core_cpu_backend::init();
-    if (ggml_backend_is_cpu(ctx->backend))
-        ggml_backend_cpu_set_n_threads(ctx->backend, params.n_threads > 0 ? params.n_threads : 4);
-    if (ggml_backend_is_cpu(ctx->backend_cpu))
-        ggml_backend_cpu_set_n_threads(ctx->backend_cpu, params.n_threads > 0 ? params.n_threads : 4);
+    if (core_cpu_backend::is_cpu(ctx->backend))
+        core_cpu_backend::set_n_threads(ctx->backend, params.n_threads > 0 ? params.n_threads : 4);
+    if (core_cpu_backend::is_cpu(ctx->backend_cpu))
+        core_cpu_backend::set_n_threads(ctx->backend_cpu, params.n_threads > 0 ? params.n_threads : 4);
 
     // ---- metadata ----
     {

src/supertonic_tts.cpp

@@ -1019,7 +1019,7 @@ struct supertonic_context* supertonic_init_from_file(const char* path_model, sup
         return nullptr;
     }
     if (core_cpu_backend::is_cpu(ctx->backend))
-        ggml_backend_cpu_set_n_threads(ctx->backend, params.n_threads > 0 ? params.n_threads : 4);
+        core_cpu_backend::set_n_threads(ctx->backend, params.n_threads > 0 ? params.n_threads : 4);
 
     if (!core_gguf::load_weights(path_model, ctx->backend, "supertonic", ctx->weights)) {
         supertonic_free(ctx);
@@ -1215,7 +1215,7 @@ void supertonic_free(struct supertonic_context* ctx) {
 
 void supertonic_set_n_threads(struct supertonic_context* ctx, int n_threads) {
     if (ctx && core_cpu_backend::is_cpu(ctx->backend) && n_threads > 0)
-        ggml_backend_cpu_set_n_threads(ctx->backend, n_threads);
+        core_cpu_backend::set_n_threads(ctx->backend, n_threads);
 }
 
 int supertonic_set_voice(struct supertonic_context* ctx, const char* voice) {

tests/test-arch-backend-map.cpp

@@ -243,6 +243,8 @@ TEST_CASE("every emitted backend name is a name a surface can open", "[unit][arc
         "dia",
         "dots-tts",
         "confucius4-tts",
+        "supertonic",
+        "fireredtts3",
         "csm",
         "parler-tts",
         "m2m100",