fix: any() in results picks the first alternative; multi-char sets stay alternations

A to-position any() lists alternative spellings; the Ruby runtime
picks the first in non-iterating mode — _repl_of now resolves the
first element (nested anys and none included).

_render_item collapsed all-string sets into a single-char class
(any("helloHelloHELLO") matches every character); sets now keep the
list form unless every string is a single character.

title_case keeps its separator: the after-separator upcasing used a
consuming match, deleting every separator occurrence.

Author: ronaldtse

src/interscript/engine.py

@@ -176,7 +176,7 @@ def _run_op(self, op: dict, text: str) -> str:
             )
             if sep != "":
                 out = re.sub(
-                    re.escape(sep) + "(.)",
+                    f"(?<={re.escape(sep)})(.)",
                     lambda m: m.group(1).upper(),
                     out,
                 )

src/interscript/isc.py

@@ -655,7 +655,9 @@ def _render_item(item: dict, aliases: dict[str, str]) -> str:
         return " + ".join(_render_item(part, aliases) for part in item["parts"])
     if kind == "set":
         items = item["items"]
-        if all(sub["type"] == "string" for sub in items):
+        if all(sub["type"] == "string" for sub in items) and all(
+            len(sub["value"]) == 1 for sub in items
+        ):
             return f'any("{_escape("".join(sub["value"] for sub in items))}")'
         return "any([" + ", ".join(_render_item(sub, aliases) for sub in items) + "])"
     if kind == "range":
@@ -751,6 +753,12 @@ def _repl_of(item: dict, aliases: dict[str, str]) -> str:
         return "".join(_repl_of(part, aliases) for part in item["parts"])
     if kind == "capture":
         return f"${item['index']}"
+    if kind == "set":
+        # A to-position any() lists alternative spellings; the Ruby
+        # runtime picks the first in non-iterating mode.
+        if not item["items"]:
+            return ""
+        return _repl_of(item["items"][0], aliases)
     if kind == "alias_ref":
         name = item["name"]
         if name not in aliases:

tests/test_isc.py

@@ -192,3 +192,22 @@ def test_title_case_word_separator():
         "kind": "title_case",
         "word_separator": "",
     }
+
+
+def test_any_in_result_picks_first_alternative():
+    src = 'system "x" { stage main { sub any("ab") any(["XA", "YB"]) } }'
+    tree = isc_to_tree(src)
+    subst = tree["stages"][0]["children"][0]
+    assert subst["result"] == "XA"
+
+
+def test_any_in_result_nested_first():
+    src = 'system "x" { stage main { sub "a" any([any("XY"), "Z"]) } }'
+    tree = isc_to_tree(src)
+    assert tree["stages"][0]["children"][0]["result"] == "X"
+
+
+def test_any_in_result_none_first():
+    src = 'system "x" { stage main { sub "a" any([none, " "]) } }'
+    tree = isc_to_tree(src)
+    assert tree["stages"][0]["children"][0]["result"] == ""