green(reify): type-fn over reify memoizes by mangled name (identity)

REIFY Phase 1.1 (Phase 1 complete). instantiateTypeFunction detects a
type-fn body that returns reify(...) (findReturnReifyCall) and routes it
to reifyType under the instantiation's name — mangled for inline use,
the alias name for `Foo :: Box(i64)` — with the type-arg bindings active
so reify payloads (`payload = T`) resolve against the instantiation args.
Placed before the general case, whose resolveTypeWithBindings would
route the reify call to the inline-position loud bail.

Registering under the mangled name lets the top-of-instantiation cache
return the SAME TypeId on a second instantiation, so Box(i64) resolved
at two independent sites is ONE type (Contract 1). examples/0615 green
(build()->consume() cross-site + `b : Box(i64) = .none`). Suite green
(671 examples, 447 unit).

current/PLAN-REIFY.md

@@ -128,7 +128,8 @@ Examples: `06xx` (comptime, deterministic), `11xx` (diagnostics for loud failure
 
 - [x] Phase 0 — `reify` flat enum (`reify(.enum(...))` mints a flat enum via the
       shared `buildEnumInfo` path; `examples/0614` green; Contract 2 confirmed)
-- [ ] Phase 1 — type-fn identity
+- [x] Phase 1 — type-fn identity (`Box :: ($T)->Type { reify(...) }` memoizes by
+      mangled name; `Box(i64)` at two sites is one type; `examples/0615` green)
 - [ ] Phase 2 — `type_info` + `field_type`
 - [ ] Phase 3 — `make_enum` + `RecvResult`/`TryResult`
 - [ ] Phase 4 — reference self-reference