iter it.1: loop/recur additive — Term::Loop/Term::Recur/LoopBinder end-to-end

Iteration-discipline milestone, 1 of 3. Adds named loop + recur as
strictly-additive first-class AST nodes: parse/print/prose/serde/
round-trip/schema lockstep, typecheck (binder typing + recur
arity/type unification via loop_stack threaded as mut.2's
mut_scope_stack; recur-tail-position via verify_loop_body), codegen
(loop-header + one phi per binder; recur back-edge br with a NEW
parallel block_terminated setter; lambda-boundary loop_frames
save/restore). Four Recur* CheckError variants. Strictly additive:
zero deletions touch tail-app/tail-do or the seven existing
block_terminated sites — this is what makes the destructive it.3
safe. recur synth = fresh metavar (resolves the plan's flagged
Type::unit() risk). loop_counter->55, loop_in_lambda->49, four
negatives fire, tail-app byte-identical, cargo test --workspace
green. Spec fda9b78, plan 7381a42.

examples/test_recur_outside_loop.ail.json

@@ -0,0 +1,34 @@
+{
+    "schema": "ailang/v0",
+    "name": "test_recur_outside_loop",
+    "imports": [],
+    "defs": [
+        {
+            "kind": "fn",
+            "name": "main",
+            "type": {
+                "k": "fn",
+                "params": [],
+                "ret": {
+                    "k": "con",
+                    "name": "Int"
+                },
+                "effects": []
+            },
+            "params": [],
+            "doc": "Iter it.1: a recur with no enclosing loop fires recur-outside-loop.",
+            "body": {
+                "t": "recur",
+                "args": [
+                    {
+                        "t": "lit",
+                        "lit": {
+                            "kind": "int",
+                            "value": 1
+                        }
+                    }
+                ]
+            }
+        }
+    ]
+}