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).

examples/expected/0615-comptime-reify-typefn-identity.exit

@@ -0,0 +1 @@
+0

examples/expected/0615-comptime-reify-typefn-identity.stderr

@@ -0,0 +1 @@
+

examples/expected/0615-comptime-reify-typefn-identity.stdout

@@ -0,0 +1,2 @@
+some 7
+none