feat: add GetSpellLink Lua API for clickable spell links in chat

Returns WoW-format spell link string "|cff71d5ff|Hspell:ID|h[Name]|h|r"
for a spell ID or name. Used by damage meters, chat addons, and WeakAuras
to create clickable spell references in chat messages.

src/addons/lua_engine.cpp

@@ -1222,6 +1222,34 @@ static int lua_UnitCreatureType(lua_State* L) {
     return 1;
 }
 
+// GetSpellLink(spellIdOrName) → "|cFFxxxxxx|Hspell:ID|h[Name]|h|r"
+static int lua_GetSpellLink(lua_State* L) {
+    auto* gh = getGameHandler(L);
+    if (!gh) { lua_pushnil(L); return 1; }
+
+    uint32_t spellId = 0;
+    if (lua_isnumber(L, 1)) {
+        spellId = static_cast<uint32_t>(lua_tonumber(L, 1));
+    } else if (lua_isstring(L, 1)) {
+        const char* name = lua_tostring(L, 1);
+        if (!name || !*name) { lua_pushnil(L); return 1; }
+        std::string nameLow(name);
+        for (char& c : nameLow) c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
+        for (uint32_t sid : gh->getKnownSpells()) {
+            std::string sn = gh->getSpellName(sid);
+            for (char& c : sn) c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
+            if (sn == nameLow) { spellId = sid; break; }
+        }
+    }
+    if (spellId == 0) { lua_pushnil(L); return 1; }
+    std::string name = gh->getSpellName(spellId);
+    if (name.empty()) { lua_pushnil(L); return 1; }
+    char link[256];
+    snprintf(link, sizeof(link), "|cff71d5ff|Hspell:%u|h[%s]|h|r", spellId, name.c_str());
+    lua_pushstring(L, link);
+    return 1;
+}
+
 // IsUsableSpell(spellIdOrName) → usable, noMana
 static int lua_IsUsableSpell(lua_State* L) {
     auto* gh = getGameHandler(L);
@@ -1685,6 +1713,7 @@ void LuaEngine::registerCoreAPI() {
         {"UnitIsEnemy",         lua_UnitIsEnemy},
         {"UnitCreatureType",    lua_UnitCreatureType},
         {"UnitClassification",  lua_UnitClassification},
+        {"GetSpellLink",         lua_GetSpellLink},
         {"IsUsableSpell",        lua_IsUsableSpell},
         {"IsInInstance",         lua_IsInInstance},
         {"GetInstanceInfo",      lua_GetInstanceInfo},