Add Warrior Charge ability with ribbon trail visual effect

Implements charge rush-to-target for spell IDs 100/6178/11578 with
smoothstep lerp movement, vertical red-orange ribbon trail, dust puffs,
client-side range validation, and sound fallback chain.

include/rendering/charge_effect.hpp

@@ -0,0 +1,107 @@
+#pragma once
+
+#include <GL/glew.h>
+#include <glm/glm.hpp>
+#include <memory>
+#include <vector>
+#include <deque>
+#include <cstdint>
+
+namespace wowee {
+namespace pipeline { class AssetManager; }
+namespace rendering {
+
+class Camera;
+class Shader;
+class M2Renderer;
+
+/// Renders a red-orange ribbon streak trailing behind the warrior during Charge,
+/// plus small dust puffs at ground level.
+class ChargeEffect {
+public:
+    ChargeEffect();
+    ~ChargeEffect();
+
+    bool initialize();
+    void shutdown();
+
+    /// Try to load M2 spell models (Charge_Caster.m2, etc.)
+    void tryLoadM2Models(M2Renderer* m2Renderer, pipeline::AssetManager* assets);
+
+    /// Start the trail (call once when charge begins)
+    void start(const glm::vec3& position, const glm::vec3& direction);
+
+    /// Feed current position each frame while charging
+    void emit(const glm::vec3& position, const glm::vec3& direction);
+
+    /// Stop adding trail points (existing ribbon fades out)
+    void stop();
+
+    /// Spawn M2 impact burst at target position
+    void triggerImpact(const glm::vec3& position);
+
+    void update(float deltaTime);
+    void render(const Camera& camera);
+
+    bool isActive() const { return emitting_ || !trail_.empty() || !dustPuffs_.empty(); }
+
+private:
+    // --- Ribbon trail ---
+    struct TrailPoint {
+        glm::vec3 center;      // World position of trail spine
+        glm::vec3 side;        // Perpendicular direction (for ribbon width)
+        float age;             // Seconds since spawned
+    };
+
+    static constexpr int MAX_TRAIL_POINTS = 64;
+    static constexpr float TRAIL_LIFETIME = 0.5f;    // Seconds before trail point fades
+    static constexpr float TRAIL_HALF_WIDTH = 0.8f;   // Half-width of ribbon
+    static constexpr float TRAIL_SPAWN_DIST = 0.4f;   // Min distance between trail points
+    std::deque<TrailPoint> trail_;
+
+    GLuint ribbonVao_ = 0;
+    GLuint ribbonVbo_ = 0;
+    std::unique_ptr<Shader> ribbonShader_;
+    std::vector<float> ribbonVerts_;  // pos(3) + alpha(1) + heat(1) = 5 floats per vert
+
+    // --- Dust puffs (small point sprites at feet) ---
+    struct DustPuff {
+        glm::vec3 position;
+        glm::vec3 velocity;
+        float lifetime;
+        float maxLifetime;
+        float size;
+        float alpha;
+    };
+
+    static constexpr int MAX_DUST = 80;
+    std::vector<DustPuff> dustPuffs_;
+
+    GLuint dustVao_ = 0;
+    GLuint dustVbo_ = 0;
+    std::unique_ptr<Shader> dustShader_;
+    std::vector<float> dustVerts_;
+
+    bool emitting_ = false;
+    glm::vec3 lastEmitPos_{0.0f};
+    float dustAccum_ = 0.0f;
+
+    // --- M2 spell effect models (optional) ---
+    static constexpr uint32_t CASTER_MODEL_ID = 999800;
+    static constexpr uint32_t IMPACT_MODEL_ID = 999801;
+    static constexpr float M2_EFFECT_DURATION = 2.0f;
+
+    M2Renderer* m2Renderer_ = nullptr;
+    bool casterModelLoaded_ = false;
+    bool impactModelLoaded_ = false;
+
+    uint32_t activeCasterInstanceId_ = 0;
+    struct ActiveM2 {
+        uint32_t instanceId;
+        float elapsed;
+    };
+    std::vector<ActiveM2> activeImpacts_;
+};
+
+} // namespace rendering
+} // namespace wowee