Add spellbook, fix WMO floor clipping, and polish UI/visuals

- Add spellbook screen (P key) with Spell.dbc name lookup and action bar assignment
- Default Attack and Hearthstone spells available in single player
- Fix WMO floor clipping (gryphon roost) by tightening ceiling rejection threshold
- Darken ocean water, increase wave motion and opacity
- Add M2 model distance fade-in to prevent pop-in
- Reposition chat window, add slash/enter key focus
- Remove debug key commands (keep only F1 perf HUD, N minimap)
- Performance: return chat history by const ref, use deque for O(1) pop_front

include/ui/spellbook_screen.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include "game/game_handler.hpp"
+#include <imgui.h>
+#include <string>
+#include <unordered_map>
+
+namespace wowee {
+
+namespace pipeline { class AssetManager; }
+
+namespace ui {
+
+class SpellbookScreen {
+public:
+    void render(game::GameHandler& gameHandler, pipeline::AssetManager* assetManager);
+    bool isOpen() const { return open; }
+    void toggle() { open = !open; }
+    void setOpen(bool o) { open = o; }
+
+private:
+    bool open = false;
+    bool pKeyWasDown = false;
+
+    // Spell name cache (loaded from Spell.dbc)
+    bool dbcLoaded = false;
+    bool dbcLoadAttempted = false;
+    std::unordered_map<uint32_t, std::string> spellNames;
+
+    // Action bar assignment
+    int assigningSlot = -1;  // Which action bar slot is being assigned (-1 = none)
+
+    void loadSpellDBC(pipeline::AssetManager* assetManager);
+    std::string getSpellName(uint32_t spellId) const;
+};
+
+} // namespace ui
+} // namespace wowee