test: comprehensive macro tests matching AGENTS.md quality bar

Expand from 20 to 47 tests (44 unit + 3 property-based) covering
all required categories:

Happy path: scalar, multi-param, string ops, boolean, CASE, table
  macros, table macro in joins, redefine
Sad path: invalid SQL, mismatched params, wrong arity, zero args,
  invalid table SQL, failed define doesn't leave partial registry
Adversarial: no params, 10 params, NULL handling, NULL propagation,
  macro composition, SQL reserved words as params, single quotes,
  Unicode, empty strings, 50 simultaneous macros
Wicked: 2000-row pipeline with filter+sort, group_by+summarise on
  1000 rows, chained macros (double→shift→clamp), table macro
  feeding into scalar macro pipeline, define/undefine/redefine cycle
Property-based: macro arithmetic matches inline SQL, define then
  list always shows macro, undefine then list never shows macro
Distributed: worker replay on single worker, macro_setup_sqls
  replayable on fresh connection, single-worker distributed matches
  local result

Also fixes: quote macro params with qi() to support SQL reserved
words as parameter names.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: cigrainger

lib/dux.ex

@@ -856,7 +856,7 @@ defmodule Dux do
   """
   def define(name, params, sql_body)
       when is_atom(name) and is_list(params) and is_binary(sql_body) do
-    param_list = Enum.map_join(params, ", ", &to_string/1)
+    param_list = Enum.map_join(params, ", ", fn p -> qi(to_string(p)) end)
     macro_name = to_string(name)
 
     create_sql =
@@ -890,7 +890,7 @@ defmodule Dux do
   """
   def define_table(name, params, sql_body)
       when is_atom(name) and is_list(params) and is_binary(sql_body) do
-    param_list = Enum.map_join(params, ", ", &to_string/1)
+    param_list = Enum.map_join(params, ", ", fn p -> qi(to_string(p)) end)
     macro_name = to_string(name)
 
     create_sql =