fix(lang): 0.R4 - ludic.ui's UiAct is its own, and a name that meets a package's export says whose it is

A game's exported UiAct collided with ludic.ui's, which nothing outside ludic.ui uses: it is private
to ludic.ui now, and a private record of one spelling in two modules never clashed. A real clash - a
type named like one a package exports - is still refused, and the message names the package and the
way out (`ludic_ui exports it, and exported names are one namespace - rename this one, or declare it
without export inside a module of your own`).

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

examples/modules/own_uiact.ludic

@@ -0,0 +1,7 @@
+# own_uiact.ludic - a game module may export a record named like one of ludic.ui's own private ones
+import "ludic.ui"
+import "own_uiact/acts"
+program OwnUiAct {
+  numbers float
+  entry { print(`{act_kind()}`) }
+}

examples/modules/own_uiact/acts/index.ludic

@@ -0,0 +1,6 @@
+module acts
+export property UiAct { kind: int = 3 }
+export function act_kind() -> int {
+  let a = new UiAct
+  return a.kind
+}

examples/rejected/pkg_export_clash.ludic

@@ -0,0 +1,7 @@
+# a program's type named like a package's export is a real clash, and the message says whose
+import "ludic.ui"
+program PkgClash {
+  numbers float
+  property UiNode { kind: int = 3 }
+  entry { print("x") }
+}