refactor(core/audio): iostream → cstdio per als missatges d'error (COUP-03)

jail_audio.hpp és un header inline que arrossegava <iostream> a cada
TU que l'incloïa, només per a std::cout de missatges d'error. <iostream>
és un include pesat i aquí no aporta res: estem fent logging simple.

Passem a <cstdio> + std::fprintf(stderr, ...) als dos fitxers (jail_audio
i audio.cpp). Missatges prefixats "Ja::funció:" / "Audio:" seguint la
convenció "Module: message" que ja fan servir director.cpp, options.cpp,
resource_cache.cpp, etc.

Efecte col·lateral: stderr és l'stream correcte per als errors (abans
anaven a stdout).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/audit-core-audio.md

@@ -62,7 +62,7 @@ Los IDs se mantienen estables una vez asignados. Cada entrada apunta al(los) fic
 |----|---------------|----------|-----------|--------|-------|
 | COUP-01 | `jail_audio.hpp:107-118` | `inline` globals en namespace: estado del engine sin encapsulación | Crítico | DEFERRED | Refactor grande; se hará en fase posterior |
 | COUP-02 | `jail_audio.hpp` entero | Engine header-only: 678 líneas compilándose en cada TU | Importante | DEFERRED | Depende de COUP-01 |
-| COUP-03 | `audio.cpp:3`, `jail_audio.hpp:8` | `#include <iostream>` sólo para `std::cout` de errores | Importante | PENDING | Sustituir por `std::fprintf(stderr,…)` con `<cstdio>` |
+| COUP-03 | `audio.cpp:3`, `jail_audio.hpp:8` | `#include <iostream>` sólo para `std::cout` de errores | Importante | DONE | `<iostream>` → `<cstdio>` als dos fitxers. `jail_audio.hpp` ja no arrossega iostream a cada TU que l'inclou. Missatges prefixats `Ja::` / `Audio:` (convenció `Module: message` del projecte) |
 | COUP-04 | `audio.cpp:43-45`, `208` | `Ja::init` en `initSDLAudio` vs `Ja::quit` en destructor (asimetría) | Menor | WONTFIX | Convive con singleton; se revisará con COUP-01 |
 | COUP-05 | `audio.hpp:71,79` | API pública expone `Ja::Music*`/`Ja::Sound*` | Menor | WONTFIX | Forward-declare ya mitiga; evita doble lookup por nombre |
 

source/core/audio/audio.cpp

@@ -3,7 +3,7 @@
 #include <SDL3/SDL.h>  // Para SDL_GetError, SDL_Init
 
 #include <algorithm>  // Para clamp
-#include <iostream>   // Para std::cout
+#include <cstdio>     // Para std::fprintf
 
 // Implementació de stb_vorbis (ha d'anar ABANS d'incloure jail_audio.hpp).
 // clang-format off
@@ -230,7 +230,7 @@ void Audio::enableMusic(bool value) {
 // Inicialitza SDL Audio
 void Audio::initSDLAudio() {
     if (!SDL_Init(SDL_INIT_AUDIO)) {
-        std::cout << "SDL_AUDIO could not initialize! SDL Error: " << SDL_GetError() << '\n';
+        std::fprintf(stderr, "Audio: SDL_AUDIO could not initialize! SDL Error: %s\n", SDL_GetError());
     } else {
         Ja::init(Defaults::Audio::FREQUENCY, Defaults::Audio::FORMAT, Defaults::Audio::CHANNELS);
         sound_enabled_ = config_.sound_enabled;

source/core/audio/jail_audio.hpp

@@ -5,7 +5,7 @@
 
 #include <algorithm>
 #include <cstdint>
-#include <iostream>
+#include <cstdio>
 #include <iterator>
 #include <memory>
 #include <string>
@@ -274,7 +274,7 @@ namespace Ja {
         audio_spec = {.format = format, .channels = num_channels, .freq = freq};
         if (sdl_audio_device != 0) { SDL_CloseAudioDevice(sdl_audio_device); }
         sdl_audio_device = SDL_OpenAudioDevice(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, &audio_spec);
-        if (sdl_audio_device == 0) { std::cout << "Failed to initialize SDL audio!" << '\n'; }
+        if (sdl_audio_device == 0) { std::fprintf(stderr, "Ja: Failed to initialize SDL audio!\n"); }
         for (auto& channel : channels) { channel.state = ChannelState::FREE; }
     }
 
@@ -305,7 +305,7 @@ namespace Ja {
             &vorbis_error,
             nullptr);
         if (music->vorbis == nullptr) {
-            std::cout << "loadMusic: stb_vorbis_open_memory failed (error " << vorbis_error << ")" << '\n';
+            std::fprintf(stderr, "Ja::loadMusic: stb_vorbis_open_memory failed (error %d)\n", vorbis_error);
             return nullptr;
         }
 
@@ -341,7 +341,7 @@ namespace Ja {
 
         current_music->stream = SDL_CreateAudioStream(&current_music->spec, &audio_spec);
         if (current_music->stream == nullptr) {
-            std::cout << "Failed to create audio stream!" << '\n';
+            std::fprintf(stderr, "Ja::playMusic: Failed to create audio stream!\n");
             current_music->state = MusicState::STOPPED;
             return;
         }
@@ -351,7 +351,7 @@ namespace Ja {
         pumpMusic(current_music);
 
         if (!SDL_BindAudioStream(sdl_audio_device, current_music->stream)) {
-            std::cout << "[ERROR] SDL_BindAudioStream failed!" << '\n';
+            std::fprintf(stderr, "Ja::playMusic: SDL_BindAudioStream failed!\n");
         }
     }
 
@@ -450,7 +450,7 @@ namespace Ja {
         stb_vorbis_seek_start(current_music->vorbis);
         current_music->stream = SDL_CreateAudioStream(&current_music->spec, &audio_spec);
         if (current_music->stream == nullptr) {
-            std::cout << "Failed to create audio stream for crossfade!" << '\n';
+            std::fprintf(stderr, "Ja::crossfadeMusic: Failed to create audio stream!\n");
             current_music->state = MusicState::STOPPED;
             return;
         }
@@ -514,7 +514,7 @@ namespace Ja {
         auto sound = std::make_unique<Sound>();
         Uint8* raw = nullptr;
         if (!SDL_LoadWAV_IO(SDL_IOFromMem(buffer, size), true, &sound->spec, &raw, &sound->length)) {
-            std::cout << "Failed to load WAV from memory: " << SDL_GetError() << '\n';
+            std::fprintf(stderr, "Ja::loadSound: Failed to load WAV from memory: %s\n", SDL_GetError());
             return nullptr;
         }
         sound->buffer.reset(raw);  // adopta el SDL_malloc'd buffer
@@ -548,7 +548,7 @@ namespace Ja {
         channels[channel].stream = SDL_CreateAudioStream(&channels[channel].sound->spec, &audio_spec);
 
         if (channels[channel].stream == nullptr) {
-            std::cout << "Failed to create audio stream for sound!" << '\n';
+            std::fprintf(stderr, "Ja::playSoundOnChannel: Failed to create audio stream!\n");
             channels[channel].state = ChannelState::FREE;
             return -1;
         }