feat(lang): L5 generic records and functions

property Pool<T> { ... }, function first<T>(xs: []T) -> T, map<T, U> over fn
types; a type writes an instance as Pool<Thing>, nested as deep as needed. The
parser names an instance Pool$Thing and remembers its generic and arguments; the
checker takes the generic declarations out, infers a call's type arguments from
its arguments or its result's declared slot, and makes each instance once as an
ordinary record or function, checked like any other. Errors print Pool<Thing>.
An instance keeps its generic's module and export (L3). ludic-fmt keeps type
arguments together while spacing comparisons and shifts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changes/generics.md

@@ -0,0 +1,8 @@
+bump: minor
+type: feature
+**Generic records and functions.** `property Pool<T> { items: []T }`, `function first<T>(xs: []T)
+-> T` and `function map<T, U>(xs: []T, f: fn(T) -> U) -> []U`; a type writes an instance as
+`Pool<Thing>`, nested as deep as needed. A call's type arguments come from its arguments, or from
+the declared type its result is written into, and are refused with the parameter named when
+neither says. Each instance is compiled once as an ordinary record or function. `ludic-fmt` keeps
+`Pool<Thing>` together while still spacing `a < b`.