Add addonperf stub module for TBC+ addon profiling API

Registers GetAddOnMemoryUsage, UpdateAddOnMemoryUsage, GetAddOnCPUUsage,
UpdateAddOnCPUUsage, ResetAddOnCPUUsage, and GetScriptCPUUsage as global
Lua functions. All stubs for now — implementation will hook lua_Alloc
and FrameScript dispatch for per-addon tracking.

src/addonperf/addonperf.zig

@@ -0,0 +1,100 @@
+//! addonperf — Expose addon memory and CPU usage to Lua.
+//!
+//! Vanilla WoW (1.12.1) lacks the TBC+ addon profiling API:
+//!   GetAddOnMemoryUsage(index|name) -> kB
+//!   UpdateAddOnMemoryUsage()
+//!   GetAddOnCPUUsage(index|name) -> ms
+//!   UpdateAddOnCPUUsage()
+//!   ResetAddOnCPUUsage(index|name)
+//!   GetScriptCPUUsage() -> enabled
+//!
+//! This module hooks the Lua engine to track per-addon memory and CPU,
+//! then registers these functions so addons like !Swatter / Blizzard_DebugTools
+//! can query performance data.
+
+const std = @import("std");
+const hook = @import("zhook");
+const logging = @import("../logging.zig");
+const mod_mutex = @import("../mutex.zig");
+
+pub const module_name: [*:0]const u8 = "addonperf";
+
+var g_mutex: ?*anyopaque = null;
+var g_is_hook_owner: bool = false;
+var log: logging.Logger = .{};
+
+pub fn isActive() bool {
+    return g_is_hook_owner;
+}
+
+// =============================================================================
+// Lua API stubs
+// =============================================================================
+
+/// GetAddOnMemoryUsage(index|"name") -> kB (float)
+/// Returns memory used by the specified addon in kilobytes.
+pub fn luaGetAddOnMemoryUsage(L: *anyopaque) callconv(.c) u32 {
+    // TODO: track per-addon Lua memory via lua_gc / allocator hooks
+    _ = L;
+    return 0; // pushes nothing — returns 0 results
+}
+
+/// UpdateAddOnMemoryUsage()
+/// Triggers a memory usage snapshot for all addons.
+pub fn luaUpdateAddOnMemoryUsage(L: *anyopaque) callconv(.c) u32 {
+    _ = L;
+    return 0;
+}
+
+/// GetAddOnCPUUsage(index|"name") -> totalMs, recentMs
+/// Returns total and recent CPU time for the specified addon.
+pub fn luaGetAddOnCPUUsage(L: *anyopaque) callconv(.c) u32 {
+    // TODO: hook FrameScript dispatch to measure per-addon handler time
+    _ = L;
+    return 0;
+}
+
+/// UpdateAddOnCPUUsage()
+/// Triggers a CPU usage snapshot for all addons.
+pub fn luaUpdateAddOnCPUUsage(L: *anyopaque) callconv(.c) u32 {
+    _ = L;
+    return 0;
+}
+
+/// ResetAddOnCPUUsage(index|"name")
+/// Resets CPU counters for the specified addon (or all if no arg).
+pub fn luaResetAddOnCPUUsage(L: *anyopaque) callconv(.c) u32 {
+    _ = L;
+    return 0;
+}
+
+/// GetScriptCPUUsage() -> enabled (1/nil)
+/// Returns whether CPU profiling is active.
+pub fn luaGetScriptCPUUsage(L: *anyopaque) callconv(.c) u32 {
+    const L_ptr = @intFromPtr(L);
+    // Always enabled when this module is loaded
+    hook.call(fn (usize, i32) callconv(hook.cc.fastcall) void, 0x6F36B0, .{ L_ptr, @as(i32, 1) }); // lua_pushboolean
+    return 1;
+}
+
+// =============================================================================
+// Install / remove
+// =============================================================================
+
+pub fn installHooks() void {
+    const result = mod_mutex.acquire(module_name);
+    g_mutex = result.handle;
+    g_is_hook_owner = result.is_owner;
+    if (!g_is_hook_owner) return;
+
+    log = logging.Logger.open(module_name, .both);
+    log.print("addonperf: stub module loaded\n");
+}
+
+pub fn removeHooks() void {
+    if (g_is_hook_owner) {
+        log.close();
+        mod_mutex.release(&g_mutex);
+    }
+    g_is_hook_owner = false;
+}