chore(release): v0.21.0 — empaquetat de recursos (AE26) i neteja de fonts

- Nou format de pack AE26 v1 (XOR + djb2), eina `pack_resources`,
  regeneració automàtica de `build/resources.pack` a cada build.
- `Resource::Helper` amb init/shutdown, fallback a disc només en Debug
  (apunta al source tree); Release exigeix pack present.
- Callers de YAML migrats a `loadFile`+deserialize des de buffer.
- Arrel neta: el pack viu a `build/`, eliminat `sync_data`.
- Placeholder font -> `ari-w9500-condensed-display`; esborrades variants
  bold/condensed no usades a `data/fonts/`.

source/game/entities/player.cpp

@@ -4,7 +4,6 @@
 
 #include <algorithm>
 #include <cmath>
-#include <fstream>
 #include <stdexcept>
 #include <utility>
 
@@ -47,18 +46,19 @@ namespace {
 }  // namespace
 
 void Player::loadFrom(const std::string& yaml_path) {
-    const auto FULL = Resource::Helper::resolve(yaml_path);
-    std::ifstream file(FULL);
-    if (!file.is_open()) {
-        throw std::runtime_error("Player: no s'ha pogut obrir " + FULL);
+    auto bytes = Resource::Helper::loadFile(yaml_path);
+    if (bytes.empty()) {
+        throw std::runtime_error("Player: no s'ha pogut obrir " + yaml_path);
     }
-    auto yaml = fkyaml::node::deserialize(file);
+    const auto* begin = reinterpret_cast<const char*>(bytes.data());
+    const auto* end = begin + bytes.size();
+    auto yaml = fkyaml::node::deserialize(begin, end);
 
     sprite_w = yaml["frameWidth"].get_value<int>();
     sprite_h = yaml["frameHeight"].get_value<int>();
 
     if (!yaml.contains("collision")) {
-        throw std::runtime_error("Player: manca bloc `collision:` a " + FULL);
+        throw std::runtime_error("Player: manca bloc `collision:` a " + yaml_path);
     }
     const auto& c = yaml["collision"];
     collision_size = c["size"].get_value<int>();