Implement flexible entity relation system (Phases A–E)

Declarative relation registry via defrelation s-expressions with
cardinality enforcement (one-to-one, one-to-many, many-to-many),
registry-aware relate/unrelate/can-relate API endpoints, generic
container-nav fragment, and relation-driven UI components.

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

shared/sexp/tests/test_components.py

@@ -264,6 +264,80 @@ class TestErrorPage:
         assert "<img" not in html
 
 
+# ---------------------------------------------------------------------------
+# ~relation-nav
+# ---------------------------------------------------------------------------
+
+class TestRelationNav:
+    def test_renders_link(self):
+        html = sexp(
+            '(~relation-nav :href "/market/farm/" :name "Farm Shop" :icon "fa fa-shopping-bag")',
+        )
+        assert 'href="/market/farm/"' in html
+        assert "Farm Shop" in html
+        assert "fa fa-shopping-bag" in html
+
+    def test_no_icon(self):
+        html = sexp(
+            '(~relation-nav :href "/cal/" :name "Events")',
+        )
+        assert 'href="/cal/"' in html
+        assert "Events" in html
+        assert "fa " not in html
+
+    def test_custom_nav_class(self):
+        html = sexp(
+            '(~relation-nav :href "/" :name "X" :nav-class "custom-class")',
+            **{"nav-class": "custom-class"},
+        )
+        assert 'class="custom-class"' in html
+
+
+# ---------------------------------------------------------------------------
+# ~relation-attach
+# ---------------------------------------------------------------------------
+
+class TestRelationAttach:
+    def test_renders_button(self):
+        html = sexp(
+            '(~relation-attach :create-url "/market/create/" :label "Add Market" :icon "fa fa-plus")',
+            **{"create-url": "/market/create/"},
+        )
+        assert 'href="/market/create/"' in html
+        assert 'hx-get="/market/create/"' in html
+        assert "Add Market" in html
+        assert "fa fa-plus" in html
+
+    def test_default_label(self):
+        html = sexp(
+            '(~relation-attach :create-url "/create/")',
+            **{"create-url": "/create/"},
+        )
+        assert "Add" in html
+
+
+# ---------------------------------------------------------------------------
+# ~relation-detach
+# ---------------------------------------------------------------------------
+
+class TestRelationDetach:
+    def test_renders_button(self):
+        html = sexp(
+            '(~relation-detach :detach-url "/api/unrelate" :name "Farm Shop")',
+            **{"detach-url": "/api/unrelate"},
+        )
+        assert 'hx-delete="/api/unrelate"' in html
+        assert 'hx-confirm="Remove Farm Shop?"' in html
+        assert "fa fa-times" in html
+
+    def test_default_name(self):
+        html = sexp(
+            '(~relation-detach :detach-url "/api/unrelate")',
+            **{"detach-url": "/api/unrelate"},
+        )
+        assert "this item" in html
+
+
 # ---------------------------------------------------------------------------
 # render_page() helper
 # ---------------------------------------------------------------------------