feat: add Lua 5.1 addon system with .toc loader and /run command

Foundation for WoW-compatible addon support:

- Vendor Lua 5.1.5 source as a static library (extern/lua-5.1.5)
- TocParser: parses .toc files (## directives + file lists)
- LuaEngine: Lua 5.1 VM with sandboxed stdlib (no io/os/debug),
  WoW-compatible print() that outputs to chat, GetTime() stub
- AddonManager: scans Data/interface/AddOns/ for .toc files,
  loads .lua files on world entry, skips LoadOnDemand addons
- /run <code> slash command for inline Lua execution
- HelloWorld test addon that prints to chat on load

Integration: AddonManager initialized after asset manager, addons
loaded once on first world entry, reset on logout. XML frame
parsing is deferred to a future step.

src/addons/toc_parser.cpp

@@ -0,0 +1,84 @@
+#include "addons/toc_parser.hpp"
+#include <fstream>
+#include <algorithm>
+
+namespace wowee::addons {
+
+std::string TocFile::getTitle() const {
+    auto it = directives.find("Title");
+    return (it != directives.end()) ? it->second : addonName;
+}
+
+std::string TocFile::getInterface() const {
+    auto it = directives.find("Interface");
+    return (it != directives.end()) ? it->second : "";
+}
+
+bool TocFile::isLoadOnDemand() const {
+    auto it = directives.find("LoadOnDemand");
+    return (it != directives.end()) && it->second == "1";
+}
+
+std::optional<TocFile> parseTocFile(const std::string& tocPath) {
+    std::ifstream f(tocPath);
+    if (!f.is_open()) return std::nullopt;
+
+    TocFile toc;
+    toc.basePath = tocPath;
+    // Strip filename to get directory
+    size_t lastSlash = tocPath.find_last_of("/\\");
+    if (lastSlash != std::string::npos) {
+        toc.basePath = tocPath.substr(0, lastSlash);
+        toc.addonName = tocPath.substr(lastSlash + 1);
+    }
+    // Strip .toc extension from addon name
+    size_t dotPos = toc.addonName.rfind(".toc");
+    if (dotPos != std::string::npos) toc.addonName.resize(dotPos);
+
+    std::string line;
+    while (std::getline(f, line)) {
+        // Strip trailing CR (Windows line endings)
+        if (!line.empty() && line.back() == '\r') line.pop_back();
+
+        // Skip empty lines
+        if (line.empty()) continue;
+
+        // ## directives
+        if (line.size() >= 3 && line[0] == '#' && line[1] == '#') {
+            std::string directive = line.substr(2);
+            size_t colon = directive.find(':');
+            if (colon != std::string::npos) {
+                std::string key = directive.substr(0, colon);
+                std::string val = directive.substr(colon + 1);
+                // Trim whitespace
+                auto trim = [](std::string& s) {
+                    size_t start = s.find_first_not_of(" \t");
+                    size_t end = s.find_last_not_of(" \t");
+                    s = (start == std::string::npos) ? "" : s.substr(start, end - start + 1);
+                };
+                trim(key);
+                trim(val);
+                if (!key.empty()) toc.directives[key] = val;
+            }
+            continue;
+        }
+
+        // Single # comment
+        if (line[0] == '#') continue;
+
+        // Whitespace-only line
+        size_t firstNonSpace = line.find_first_not_of(" \t");
+        if (firstNonSpace == std::string::npos) continue;
+
+        // File entry — normalize backslashes to forward slashes
+        std::string filename = line.substr(firstNonSpace);
+        size_t lastNonSpace = filename.find_last_not_of(" \t");
+        if (lastNonSpace != std::string::npos) filename.resize(lastNonSpace + 1);
+        std::replace(filename.begin(), filename.end(), '\\', '/');
+        toc.files.push_back(std::move(filename));
+    }
+
+    return toc;
+}
+
+} // namespace wowee::addons