iter mq.1: class-ref canonical-form extension + workspace-internal class-name qualification

Three schema fields move bare → canonical (bare for same-module,
<module>.<Class> for cross-module): InstanceDef.class,
Constraint.class, SuperclassRef.class. Symmetric to ct.1's
Type::Con.name rule. ClassDef.name stays bare.

validate_canonical_type_names gains three field-walks via new
check_class_ref helper + two sibling diagnostics
BareCrossModuleClassRef / BadCrossModuleClassRef.
check_class_name_fields narrowed to ClassDef.name-only.

Workspace-internal class-name keys all qualified:
class_def_module, class_by_name, registry entries.0,
ClassMethodEntry.class_name, class_superclasses, mono's
class_index, Origin::Class.class_name. New qualify_class_ref
helper at workspace.rs scope plus sibling
qualify_class_ref_in_check in ailang-check.

Two new positive on-disk fixtures (mq1_xmod_constraint_class{,_dep})
exercise the qualified Constraint.class shape.

Recon claim that all existing fixtures' class-refs are intra-module
was empirically wrong — 10 fixtures required minimal canonical-form
migration. Duplicate-instance test architecturally restructured:
post-mq.1 orphan-freedom makes two-modules-on-same-(class,type)
structurally impossible; new test_22b1_dup_same_module fixture
lands both instances in the class's module.

Plan defects fixed inline: Origin::Class.class_name single
construction site (plan recon off-by-one); build_class_index in
mono.rs needed qualifying; build_module_globals needed Def::Instance
carve-out; check_fn declared-constraint matching needed inline
canonical-form lifting; NoInstance Float-aware message arm needed
prelude.Eq/prelude.Ord match; coherence type-leg needed qualified-
head split-and-lookup. Tasks 3-6 ran as one coherent fix.

7/7 tasks, 520 tests green. bench/compile_check.py + cross_lang.py
exit 0; bench/check.py exit 1 (4 improvements-beyond-tolerance,
audit-ratifiable, not a regression).

MethodNameCollision + dispatch path unchanged; iters mq.2 + mq.3
land them.

examples/cmp_max_smoke.ail.json

@@ -9,7 +9,7 @@
       "type": {
         "k": "forall",
         "vars": ["a"],
-        "constraints": [{ "class": "Ord", "type": { "k": "var", "name": "a" } }],
+        "constraints": [{ "class": "prelude.Ord", "type": { "k": "var", "name": "a" } }],
         "body": {
           "k": "fn",
           "params": [{ "k": "var", "name": "a" }, { "k": "var", "name": "a" }],

examples/ctt2_collision_lib.ail.json

@@ -10,7 +10,7 @@
     },
     {
       "kind": "instance",
-      "class": "MyC",
+      "class": "ctt2_collision_cls.MyC",
       "type": { "k": "con", "name": "Foo" },
       "methods": [
         {

examples/ctt2_collision_main.ail.json

@@ -13,7 +13,7 @@
     },
     {
       "kind": "instance",
-      "class": "MyC",
+      "class": "ctt2_collision_cls.MyC",
       "type": { "k": "con", "name": "Foo" },
       "methods": [
         {

examples/eq_ord_polymorphic.ail.json

@@ -10,7 +10,7 @@
       "type": {
         "k": "forall",
         "vars": ["a"],
-        "constraints": [{ "class": "Ord", "type": { "k": "var", "name": "a" } }],
+        "constraints": [{ "class": "prelude.Ord", "type": { "k": "var", "name": "a" } }],
         "body": {
           "k": "fn",
           "params": [

examples/eq_ord_user_adt.ail.json

@@ -14,7 +14,7 @@
     },
     {
       "kind": "instance",
-      "class": "Eq",
+      "class": "prelude.Eq",
       "type": { "k": "con", "name": "IntBox" },
       "doc": "Eq IntBox by structural unwrap of the inner Int.",
       "methods": [
@@ -56,7 +56,7 @@
     },
     {
       "kind": "instance",
-      "class": "Ord",
+      "class": "prelude.Ord",
       "type": { "k": "con", "name": "IntBox" },
       "doc": "Ord IntBox by delegating to Int's compare on the inner field.",
       "methods": [

examples/mq1_xmod_constraint_class.ail.json

@@ -0,0 +1,29 @@
+{
+  "schema": "ailang/v0",
+  "name": "mq1_xmod_constraint_class",
+  "imports": [{ "module": "mq1_xmod_constraint_class_dep" }],
+  "defs": [
+    {
+      "kind": "fn",
+      "name": "useShow",
+      "doc": "Positive mq.1 fixture: a polymorphic fn that takes a single value and a Show constraint, ignores the value, and returns Unit. Exercises the qualified `Constraint.class` shape end-to-end (loader + validator + check_workspace).",
+      "type": {
+        "k": "forall",
+        "vars": ["a"],
+        "constraints": [
+          { "class": "mq1_xmod_constraint_class_dep.Show",
+            "type": { "k": "var", "name": "a" } }
+        ],
+        "body": {
+          "k": "fn",
+          "params": [{ "k": "var", "name": "a" }],
+          "param_modes": ["borrow"],
+          "ret": { "k": "con", "name": "Unit" },
+          "effects": []
+        }
+      },
+      "params": ["_x"],
+      "body": { "t": "lit", "lit": { "kind": "unit" } }
+    }
+  ]
+}

examples/mq1_xmod_constraint_class_dep.ail.json

@@ -0,0 +1,23 @@
+{
+  "schema": "ailang/v0",
+  "name": "mq1_xmod_constraint_class_dep",
+  "imports": [],
+  "defs": [
+    {
+      "kind": "class",
+      "name": "Show",
+      "param": "a",
+      "methods": [
+        {
+          "name": "show",
+          "type": {
+            "k": "fn",
+            "params": [{ "k": "var", "name": "a" }],
+            "ret": { "k": "con", "name": "Str" },
+            "effects": []
+          }
+        }
+      ]
+    }
+  ]
+}

examples/test_22b1_dup_a.ail.json

@@ -4,36 +4,15 @@
   "imports": [
     {
       "module": "test_22b1_dup_b"
+    },
+    {
+      "module": "test_22b1_dup_classmod"
     }
   ],
   "defs": [
-    {
-      "kind": "class",
-      "name": "Show",
-      "param": "a",
-      "methods": [
-        {
-          "name": "show",
-          "type": {
-            "k": "fn",
-            "params": [
-              {
-                "k": "var",
-                "name": "a"
-              }
-            ],
-            "ret": {
-              "k": "con",
-              "name": "Str"
-            },
-            "effects": []
-          }
-        }
-      ]
-    },
     {
       "kind": "instance",
-      "class": "Show",
+      "class": "test_22b1_dup_classmod.Show",
       "type": {
         "k": "con",
         "name": "test_22b1_dup_b.MyInt"
@@ -52,4 +31,4 @@
       ]
     }
   ]
-}
+}

examples/test_22b1_dup_b.ail.json

@@ -1,7 +1,9 @@
 {
   "schema": "ailang/v0",
   "name": "test_22b1_dup_b",
-  "imports": [],
+  "imports": [
+    { "module": "test_22b1_dup_classmod" }
+  ],
   "defs": [
     {
       "kind": "type",
@@ -15,7 +17,7 @@
     },
     {
       "kind": "instance",
-      "class": "Show",
+      "class": "test_22b1_dup_classmod.Show",
       "type": { "k": "con", "name": "MyInt" },
       "methods": [
         {

examples/test_22b1_dup_classmod.ail.json

@@ -0,0 +1,23 @@
+{
+  "schema": "ailang/v0",
+  "name": "test_22b1_dup_classmod",
+  "imports": [],
+  "defs": [
+    {
+      "kind": "class",
+      "name": "Show",
+      "param": "a",
+      "methods": [
+        {
+          "name": "show",
+          "type": {
+            "k": "fn",
+            "params": [{ "k": "var", "name": "a" }],
+            "ret": { "k": "con", "name": "Str" },
+            "effects": []
+          }
+        }
+      ]
+    }
+  ]
+}

examples/test_22b1_dup_entry.ail.json

@@ -3,7 +3,8 @@
   "name": "test_22b1_dup_entry",
   "imports": [
     { "module": "test_22b1_dup_a" },
-    { "module": "test_22b1_dup_b" }
+    { "module": "test_22b1_dup_b" },
+    { "module": "test_22b1_dup_classmod" }
   ],
   "defs": []
 }

examples/test_22b1_dup_same_module.ail.json

@@ -0,0 +1,45 @@
+{
+  "schema": "ailang/v0",
+  "name": "test_22b1_dup_same_module",
+  "imports": [],
+  "defs": [
+    {
+      "kind": "class",
+      "name": "Show",
+      "param": "a",
+      "methods": [
+        {
+          "name": "show",
+          "type": {
+            "k": "fn",
+            "params": [{ "k": "var", "name": "a" }],
+            "ret": { "k": "con", "name": "Str" },
+            "effects": []
+          }
+        }
+      ]
+    },
+    {
+      "kind": "instance",
+      "class": "Show",
+      "type": { "k": "con", "name": "Int" },
+      "methods": [
+        {
+          "name": "show",
+          "body": { "t": "lit", "lit": { "kind": "str", "value": "first" } }
+        }
+      ]
+    },
+    {
+      "kind": "instance",
+      "class": "Show",
+      "type": { "k": "con", "name": "Int" },
+      "methods": [
+        {
+          "name": "show",
+          "body": { "t": "lit", "lit": { "kind": "str", "value": "second" } }
+        }
+      ]
+    }
+  ]
+}

examples/test_22b1_orphan_third.ail.json

@@ -7,7 +7,7 @@
   "defs": [
     {
       "kind": "instance",
-      "class": "Show",
+      "class": "test_22b1_orphan_third_classmod.Show",
       "type": { "k": "con", "name": "Int" },
       "methods": [
         {

examples/test_22b2_unbound_constraint_var.ail.json

@@ -3,6 +3,12 @@
   "name": "test_22b2_unbound_constraint_var",
   "imports": [],
   "defs": [
+    {
+      "kind": "class",
+      "name": "Bar",
+      "param": "x",
+      "methods": []
+    },
     {
       "kind": "class",
       "name": "Foo",