fix: any_character converts to the Stdlib any-char alias

The :any_char fragment had no transform rule and stringified to
"any_charany_character" — odni-uzb's five geminate-collapse rules
(capture(any_character) + ref(1) -> ref(1)) compiled to garbage and
"ччччч" became "chchchchch" instead of "ch". Converts to
AliasRef(:any_character), which the runtime resolves to Stdlib's ".".

odni-uzb: 18 examples, 0 failures (was 6). Sweep tail: 38 -> 32.

Author: ronaldtse

lib/interscript/isc/transform.rb

@@ -23,6 +23,9 @@ class Transform < Parsanol::Transform
       rule(identifier: simple(:i)) { i.to_s }
 
       rule(none: simple(:_)) { Items::None.new }
+      # any_character is the Stdlib any-char alias (".") — without this
+      # rule the fragment stringified to "any_charany_character".
+      rule(any_char: simple(:_)) { Items::AliasRef.new("any_character") }
       rule(primitive: simple(:p)) { Items::Primitive.new(p.to_s) }
       rule(function: simple(:f)) { Items::Function.new(f.to_s) }
       rule(alias: {identifier: simple(:n), qualified_name: simple(:q)}) {

spec/interscript/isc/node_adapter_spec.rb

@@ -395,3 +395,29 @@ def parse_and_adapt(src)
     expect(calls).to eq(%i[decompose compose])
   end
 end
+
+RSpec.describe "NodeAdapter any_character" do
+  it "converts to the Stdlib any-character alias, not a stringified fragment" do
+    src = <<~ISC
+      system "t:a-b:C-D:1" {
+        metadata { name "T" }
+        stage main {
+          sub {
+            from capture(any_character) + ref(1)
+            to ref(1)
+          }
+        }
+      }
+    ISC
+    node = Interscript::Isc::NodeAdapter.to_interscript_node(
+      Interscript::Isc::DocumentBuilder.build(Interscript::Isc::Parser.parse(src))
+    )
+    inner = node.stages[:main].children.first.from.children.first.data
+    expect(inner).to be_a(Interscript::Node::Item::Alias)
+    expect(inner.name).to eq(:any_character)
+    interp = Interscript::Interpreter.new
+    interp.compile(node)
+    # The geminate collapse: any char followed by itself collapses to one.
+    expect(interp.call("чч")).to eq("ч")
+  end
+end