Add marker persistence, proximity respawn, and group sync

Markers now survive zone transitions via persistent MarkerDef structs
(position + area ID) that are NOT cleared during world teardown. The
per-frame tick detects zombie entities (refcount <= 1 from game culling)
and respawns markers when the player approaches within 200 yards.

New DLL Lua APIs: SetMarkerDef, ClearMarkerDef, GetMarkerDef for the
addon to store/query definitions without immediate entity creation.

Addon layer adds group sync via CHAT_MSG_ADDON messages using colon-
delimited protocol (P:idx:x:y:z:area, C:idx, CA, SR, SF:...). Wraps
WorldMarker/ClearWorldMarker to broadcast on placement. Permission
model: raid leader/assist or party leader only.

Fix lua_pushnumber calling convention: Ghidra confirms it is thiscall
(ECX=L, f64 on stack [EBP+8]/[EBP+0xc], ret 8), not fastcall. The
patched inreg fastcall was shoving the f64's low dword into EDX,
producing garbage values like 1.17e-250 from 1810.

src/main.zig

@@ -107,7 +107,8 @@ pub const lua = struct {
     }
 
     pub fn pushnumber(L: State, n: f64) void {
-        const f: *const fn (State, f64) callconv(fc) void = @ptrFromInt(0x6F3810);
+        // __thiscall: ECX=L, f64 on stack [EBP+8]/[EBP+0xc], ret 8.
+        const f: *const fn (State, f64) callconv(.{ .x86_thiscall = .{} }) void = @ptrFromInt(0x6F3810);
         f(L, n);
     }
 
@@ -263,6 +264,9 @@ fn registerLuaFunctions() void {
         registerFunction("ClearWorldMarker", @intFromPtr(&markers.luaClearWorldMarker));
         registerFunction("GetPlayerPosition", @intFromPtr(&markers.luaGetPlayerPosition));
         registerFunction("DistanceToMark", @intFromPtr(&markers.luaDistanceToMark));
+        registerFunction("SetMarkerDef", @intFromPtr(&markers.luaSetMarkerDef));
+        registerFunction("ClearMarkerDef", @intFromPtr(&markers.luaClearMarkerDef));
+        registerFunction("GetMarkerDef", @intFromPtr(&markers.luaGetMarkerDef));
     }
 }