Fix quasiquote flattening bug, decouple relations from evaluator

- Fix qq-expand in eval.sx: use concat+list instead of append to prevent
  nested lists from being flattened during quasiquote expansion
- Update append primitive to match spec ("if x is list, concatenate")
- Rebuild sx_ref.py with quasiquote fix
- Make relations.py self-contained: parse defrelation AST directly
  without depending on the evaluator (25/25 tests pass)
- Replace hand-written JSEmitter with js.sx self-hosting bootstrapper
- Guard server-only tests in test-eval.sx with runtime check

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/tests/test_relations.py

@@ -2,11 +2,12 @@
 
 import pytest
 
-from shared.sx.evaluator import evaluate, EvalError
 from shared.sx.parser import parse
 from shared.sx.relations import (
+    RelationError,
     _RELATION_REGISTRY,
     clear_registry,
+    evaluate_defrelation,
     get_relation,
     load_relation_registry,
     relations_from,
@@ -38,7 +39,7 @@ class TestDefrelation:
               :nav-icon "fa fa-shopping-bag"
               :nav-label "markets")
         ''')
-        result = evaluate(tree)
+        result = evaluate_defrelation(tree)
         assert isinstance(result, RelationDef)
         assert result.name == "page->market"
         assert result.from_type == "page"
@@ -54,7 +55,7 @@ class TestDefrelation:
             (defrelation :a->b
               :from "a" :to "b" :cardinality :one-to-one :nav :hidden)
         ''')
-        evaluate(tree)
+        evaluate_defrelation(tree)
         assert get_relation("a->b") is not None
         assert get_relation("a->b").cardinality == "one-to-one"
 
@@ -64,7 +65,7 @@ class TestDefrelation:
               :from "page" :to "menu_node"
               :cardinality :one-to-one :nav :hidden)
         ''')
-        result = evaluate(tree)
+        result = evaluate_defrelation(tree)
         assert result.cardinality == "one-to-one"
         assert result.inverse is None
         assert result.nav == "hidden"
@@ -79,7 +80,7 @@ class TestDefrelation:
               :nav-icon "fa fa-file-alt"
               :nav-label "events")
         ''')
-        result = evaluate(tree)
+        result = evaluate_defrelation(tree)
         assert result.cardinality == "many-to-many"
 
     def test_default_nav_is_hidden(self):
@@ -87,7 +88,7 @@ class TestDefrelation:
             (defrelation :x->y
               :from "x" :to "y" :cardinality :one-to-many)
         ''')
-        result = evaluate(tree)
+        result = evaluate_defrelation(tree)
         assert result.nav == "hidden"
 
     def test_invalid_cardinality_raises(self):
@@ -95,42 +96,42 @@ class TestDefrelation:
             (defrelation :bad
               :from "a" :to "b" :cardinality :wrong)
         ''')
-        with pytest.raises(EvalError, match="invalid cardinality"):
-            evaluate(tree)
+        with pytest.raises(RelationError, match="invalid cardinality"):
+            evaluate_defrelation(tree)
 
     def test_invalid_nav_raises(self):
         tree = parse('''
             (defrelation :bad
               :from "a" :to "b" :cardinality :one-to-one :nav :bogus)
         ''')
-        with pytest.raises(EvalError, match="invalid nav"):
-            evaluate(tree)
+        with pytest.raises(RelationError, match="invalid nav"):
+            evaluate_defrelation(tree)
 
     def test_missing_from_raises(self):
         tree = parse('''
             (defrelation :bad :to "b" :cardinality :one-to-one)
         ''')
-        with pytest.raises(EvalError, match="missing required :from"):
-            evaluate(tree)
+        with pytest.raises(RelationError, match="missing required :from"):
+            evaluate_defrelation(tree)
 
     def test_missing_to_raises(self):
         tree = parse('''
             (defrelation :bad :from "a" :cardinality :one-to-one)
         ''')
-        with pytest.raises(EvalError, match="missing required :to"):
-            evaluate(tree)
+        with pytest.raises(RelationError, match="missing required :to"):
+            evaluate_defrelation(tree)
 
     def test_missing_cardinality_raises(self):
         tree = parse('''
             (defrelation :bad :from "a" :to "b")
         ''')
-        with pytest.raises(EvalError, match="missing required :cardinality"):
-            evaluate(tree)
+        with pytest.raises(RelationError, match="missing required :cardinality"):
+            evaluate_defrelation(tree)
 
     def test_name_must_be_keyword(self):
         tree = parse('(defrelation "not-keyword" :from "a" :to "b" :cardinality :one-to-one)')
-        with pytest.raises(EvalError, match="must be a keyword"):
-            evaluate(tree)
+        with pytest.raises(RelationError, match="must be a keyword"):
+            evaluate_defrelation(tree)
 
 
 # ---------------------------------------------------------------------------
@@ -154,7 +155,7 @@ class TestRegistry:
                 :from "page" :to "menu_node" :cardinality :one-to-one
                 :nav :hidden))
         ''')
-        evaluate(tree)
+        evaluate_defrelation(tree)
 
     def test_get_relation(self):
         self._load_sample()