iter form-a.0: prelude pilot — examples/prelude.ail rendered

First iteration of the form-a-default-authoring milestone. Mechanical:
one `ail render examples/prelude.ail.json > examples/prelude.ail`
captures the canonical Form-A projection (116 lines / 6386 bytes).
No source-code edits, no test edits.

The two auto-discovering roundtrip tests in
crates/ailang-surface/tests/round_trip.rs pick up the new fixture
via read_dir without test changes and both pass:
- every_ail_fixture_matches_its_json_counterpart — the .ail parses
  to canonical bytes byte-equal to prelude.ail.json (gate test).
- parse_then_print_then_parse_is_idempotent_on_every_ail_fixture —
  the Form-A printer is idempotent over prelude.

cargo test --workspace green at 558 tests (identical to pre-iter
baseline; audit-24 / iter-24.tidy lineage).

prelude.ail.json retained per spec §A2 — this is the singular
dual-form iter; iter 1 deletes it alongside the bulk test-infra
refactor.

Zero re-loops, zero review-phase repairs. Recon predictions matched
reality exactly (116 lines, 6386 bytes, `(module prelude` header,
558-test baseline). Strong signal that the iter-1+ bulk migration
mechanism is sound.

examples/prelude.ail

@@ -0,0 +1,116 @@
+(module prelude
+  (data Ordering
+    (doc "Result of a three-way comparison: LT (less than), EQ (equal), GT (greater than). Ships in milestone 23 as the codomain of Ord.compare.")
+    (ctor LT)
+    (ctor EQ)
+    (ctor GT))
+  (class Eq
+    (param a)
+    (doc "Structural equality. Ships in milestone 23 alongside Ord. The primitive `==` operator stays as the surface-level comparator this iter; routing `==` through `Eq.eq` is the declared P2 follow-up (see docs/specs/2026-05-10-23-eq-ord-prelude.md, `Out of scope`).")
+    (method eq
+      (type (fn-type (params (borrow a) (borrow a)) (ret (con Bool))))))
+  (instance
+    (class Eq)
+    (type (con Int))
+    (doc "Eq Int. Body lowers to `icmp eq i64` via the existing primitive `==` dispatch in `lower_eq`.")
+    (method eq
+      (body (lam (params (typed x a) (typed y a)) (ret (con Bool)) (body (app == x y))))))
+  (instance
+    (class Eq)
+    (type (con Bool))
+    (doc "Eq Bool. Body lowers to `icmp eq i1` via the existing primitive `==` dispatch in `lower_eq`.")
+    (method eq
+      (body (lam (params (typed x a) (typed y a)) (ret (con Bool)) (body (app == x y))))))
+  (instance
+    (class Eq)
+    (type (con Str))
+    (doc "Eq Str. The lambda body shape mirrors Int/Bool for round-trip stability, but the codegen intercept in `emit_fn` overrides the body to call `@ail_str_eq` directly — see `try_emit_primitive_instance_body` in `crates/ailang-codegen/src/lib.rs`.")
+    (method eq
+      (body (lam (params (typed x a) (typed y a)) (ret (con Bool)) (body (app == x y))))))
+  (class Ord
+    (param a)
+    (superclass (class Eq) (type a))
+    (doc "Total ordering. Ships in milestone 23 alongside Eq. `compare x y` returns LT, EQ, or GT (the three-ctor Ordering ADT also in the prelude). Decision 11's single-superclass closure requires `instance Eq T` for every `instance Ord T` — the three Ord instances below pair with the three Eq instances shipped in iter 23.2.3.")
+    (method compare
+      (type (fn-type (params (borrow a) (borrow a)) (ret (con Ordering))))))
+  (instance
+    (class Ord)
+    (type (con Int))
+    (doc "Ord Int. The lambda body shape is a placeholder for round-trip stability; the codegen intercept `try_emit_primitive_instance_body::\"compare__Int\"` emits a three-way `icmp slt` / `icmp eq` branch ladder constructing LT / EQ / GT.")
+    (method compare
+      (body (lam (params (typed x a) (typed y a)) (ret (con Ordering)) (body (term-ctor Ordering EQ))))))
+  (instance
+    (class Ord)
+    (type (con Bool))
+    (doc "Ord Bool. Body lowered via `try_emit_primitive_instance_body::\"compare__Bool\"` — `icmp ult i1` LT-test, `icmp eq i1` EQ-test, GT default.")
+    (method compare
+      (body (lam (params (typed x a) (typed y a)) (ret (con Ordering)) (body (term-ctor Ordering EQ))))))
+  (instance
+    (class Ord)
+    (type (con Str))
+    (doc "Ord Str. Body lowered via `try_emit_primitive_instance_body::\"compare__Str\"` — `call i32 @ail_str_compare(ptr, ptr)` then branch on slt-0 / eq-0 against the normalised {-1, 0, +1} return.")
+    (method compare
+      (body (lam (params (typed x a) (typed y a)) (ret (con Ordering)) (body (term-ctor Ordering EQ))))))
+  (class Show
+    (param a)
+    (doc "Producer of a human-readable Str representation. Ships in milestone 24 with primitive instances for Int/Bool/Str/Float; user types declare their own instance.")
+    (method show
+      (type (fn-type (params (borrow a)) (ret (con Str))))))
+  (instance
+    (class Show)
+    (type (con Int))
+    (method show
+      (body (lam (params (typed x (con Int))) (ret (con Str)) (body (app int_to_str x))))))
+  (instance
+    (class Show)
+    (type (con Bool))
+    (method show
+      (body (lam (params (typed x (con Bool))) (ret (con Str)) (body (app bool_to_str x))))))
+  (instance
+    (class Show)
+    (type (con Str))
+    (method show
+      (body (lam (params (typed x (con Str))) (ret (con Str)) (body (app str_clone x))))))
+  (instance
+    (class Show)
+    (type (con Float))
+    (method show
+      (body (lam (params (typed x (con Float))) (ret (con Str)) (body (app float_to_str x))))))
+  (fn ne
+    (doc "Polymorphic disequality. `ne x y` ≡ not (eq x y). Ships in milestone 23 as the Eq-class free helper.")
+    (type (forall (vars a) (constraints (constraint Eq a)) (fn-type (params (borrow a) (borrow a)) (ret (con Bool)))))
+    (params x y)
+    (body (app not (app eq x y))))
+  (fn lt
+    (doc "Polymorphic strict-less-than. `lt x y` ≡ case compare x y of LT -> True; _ -> False. Ships in milestone 23 as the Ord-class free helper.")
+    (type (forall (vars a) (constraints (constraint Ord a)) (fn-type (params (borrow a) (borrow a)) (ret (con Bool)))))
+    (params x y)
+    (body (match (app compare x y)
+      (case (pat-ctor LT) true)
+      (case _ false))))
+  (fn le
+    (doc "Polymorphic less-than-or-equal. `le x y` ≡ case compare x y of GT -> False; _ -> True. Ships in milestone 23 as the Ord-class free helper.")
+    (type (forall (vars a) (constraints (constraint Ord a)) (fn-type (params (borrow a) (borrow a)) (ret (con Bool)))))
+    (params x y)
+    (body (match (app compare x y)
+      (case (pat-ctor GT) false)
+      (case _ true))))
+  (fn gt
+    (doc "Polymorphic strict-greater-than. `gt x y` ≡ case compare x y of GT -> True; _ -> False. Ships in milestone 23 as the Ord-class free helper.")
+    (type (forall (vars a) (constraints (constraint Ord a)) (fn-type (params (borrow a) (borrow a)) (ret (con Bool)))))
+    (params x y)
+    (body (match (app compare x y)
+      (case (pat-ctor GT) true)
+      (case _ false))))
+  (fn ge
+    (doc "Polymorphic greater-than-or-equal. `ge x y` ≡ case compare x y of LT -> False; _ -> True. Ships in milestone 23 as the Ord-class free helper.")
+    (type (forall (vars a) (constraints (constraint Ord a)) (fn-type (params (borrow a) (borrow a)) (ret (con Bool)))))
+    (params x y)
+    (body (match (app compare x y)
+      (case (pat-ctor LT) false)
+      (case _ true))))
+  (fn print
+    (doc "Polymorphic console-print helper. `print x` ≡ `do io/print_str (show x)` with an explicit let-binder around `show x` for heap-Str RC discipline per eob.1 Str carve-out. Ships in milestone 24 as the second half of the Show prelude.")
+    (type (forall (vars a) (constraints (constraint Show a)) (fn-type (params (borrow a)) (ret (con Unit)) (effects IO))))
+    (params x)
+    (body (let s (app show x) (do io/print_str s)))))