feat(audio): add YuE2 music generation (#12617)

* feat(audio): forward sound generation params

Pass string-valued sound generation parameters from the public request to
the audio backend. Typed fields retain precedence over colliding generic
parameters, and source audio remains unavailable in the public schema.

Assisted-by: nib:gpt-5.6-sol
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

* feat(gallery): add YuE2 music model

Assisted-by: nib:gpt-5.6-sol
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

* docs(audio): document YuE2 sound generation

Assisted-by: nib:gpt-5.6-sol
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

* fix(audio): reserve source input parameter

Assisted-by: nib:gpt-5.6-sol
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

---------

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

backend/cpp/audio-cpp/generation_request.cpp

@@ -170,6 +170,17 @@ build_sound_generation_request(const backend::SoundGenerationRequest &request,
         task.audio_input = std::move(*source_audio);
     }
 
+    // Generic options are copied first so typed request fields remain authoritative
+    // when callers provide the same key in both places.
+    for (const auto &param : request.params()) {
+        // src is reserved for trusted, decoded source audio and must not cross
+        // the generic option boundary as a caller-controlled filesystem path.
+        if (param.first == "src") {
+            continue;
+        }
+        task.options[param.first] = param.second;
+    }
+
     // WHAT LANDS AND WHAT DOES NOT. Three families advertise AudioGeneration in
     // the pinned upstream: ace_step, heartmula and stable_audio. Every key below
     // was grepped against find_option/parse_*_option in src/ and include/ rather