feat: cite option lists as choices_from

RetroBat's es_features.cfg and KNULLI's es_features.yml list the values
a menu offers. They move out of source_ref into choices_from, beside the
generator that writes the choice. RetroBat's xemu flashrom record holds
outside a Chihiro launch (Xemu.Generator.cs:48, 284), and KNULLI's
libretro boot disk records name the one core es_features offers them
for. Rescraped at the pinned revisions.

scripts/scraper/knulli_launchers.py

@@ -1001,6 +1001,14 @@ def boot_disks(
         emulator = (
             ", ".join(_caller_cores(cg, spec.caller)) if spec.caller else cg.emulator(module)
         )
+        if spec.caller and spec.feature[:2] == ("libretro", "cores"):
+            # The option is offered for one core of the system: es_features
+            # lists it under that core, the other cores the generator serves
+            # never see it (KNULLI's macintosh offers mame alone).
+            core = spec.feature[2]
+            if core not in emulator.split(", "):
+                src.fail(f"es_features offers the option for {core}, which the generator does not serve")
+            emulator = core
         found = 0
         for chain in ast.walk(src.tree):
             if not (
@@ -1054,10 +1062,10 @@ def boot_disks(
                     expands={option: values}, case_insensitive=False, search_dir=cg.bios,
                     passes_to=f"command line {flag}", fails_when_missing=False,
                     depends_on_option=f"{option} ({' and '.join(tests)})",
-                    source_ref=", ".join([
-                        src.ref([*spans, src.span(statement), _lines(added)]),
-                        f"{ES_FEATURES}:{lines[0]}-{lines[1]}" if not listed else "",
-                    ]).rstrip(", "),
+                    # The values the menu offers come from es_features.yml;
+                    # the generator writing the choice is the evidence.
+                    choices_from=None if listed else f"{ES_FEATURES}:{lines[0]}-{lines[1]}",
+                    source_ref=src.ref([*spans, src.span(statement), _lines(added)]),
                 ))
         if not found:
             src.fail("names no BIOS file from an option value")

scripts/scraper/retrobat_launchers.py

@@ -14,6 +14,11 @@ import bisect
 import re
 from collections.abc import Callable, Iterator
 
+try:
+    from .shell_launchers import is_feature_ref, split_ref
+except ImportError:
+    from shell_launchers import is_feature_ref, split_ref  # type: ignore[no-redef]
+
 GENERATORS = "emulatorLauncher/Generators"
 FEATURES = ".emulationstation/es_features.cfg"
 
@@ -1254,6 +1259,11 @@ def xemu(sources: dict[str, Source]) -> list[Record]:
     )
 
     flash = src.find(r'isOptSet\("(xemu_flashrom)"\)', "xemu_flashrom")
+    # The flashrom is written outside a Chihiro launch only.
+    chihiro_set = src.find(r"(_chihiro) = \(([^;]+)\);", "Chihiro test")
+    chihiro_guard = src.find_all(
+        rf"if \(!{chihiro_set.group(1)}\)", "flashrom guard", end=flash.start()
+    )[-1]
     flash_default = src.find(
         r'ini\.WriteValue\("([\w.]+)", "(flashrom_path)", "\'" \+ Path\.Combine\(flashromPath, "([^"]+)"\)',
         "flashrom default",
@@ -1267,7 +1277,10 @@ def xemu(sources: dict[str, Source]) -> list[Record]:
             "core_option",
             _unique([flash_default.group(3), *choices]),
             source_ref(
-                (src.path, [src.lines(flash.start(), flash_default.end())]),
+                (src.path, [
+                    src.lines(chihiro_set.start(), chihiro_set.end()),
+                    src.lines(chihiro_guard.start(), flash_default.end()),
+                ]),
                 (features.path, [choice_lines]),
             ),
             case_insensitive=True,
@@ -1277,7 +1290,7 @@ def xemu(sources: dict[str, Source]) -> list[Record]:
                 f" default {flash_default.group(3)}"
             ),
             fails_when_missing="path written without an existence check",
-            depends_on_option=flash.group(1),
+            depends_on_option=f"{flash.group(1)}, not ({chihiro_set.group(2)})",
         )
     )
 
@@ -3890,4 +3903,23 @@ def extract_launchers(texts: dict[str, str]) -> list[Record]:
     if missing:
         raise LauncherPatternMissing(missing[0], "source file")
     sources = {path: Source(path, text) for path, text in texts.items()}
-    return [record for extractor in EXTRACTORS for record in extractor(sources)]
+    return [
+        _choices_apart(record) for extractor in EXTRACTORS for record in extractor(sources)
+    ]
+
+
+def _choices_apart(record: Record) -> Record:
+    """The es_features.cfg part of a record's source_ref, moved to choices_from.
+
+    The feature file lists the values a menu option offers. The generator
+    writing the choice is the record's evidence, never the list.
+    """
+    parts = split_ref(str(record["source_ref"]))
+    listed = [p for p in parts if is_feature_ref(p)]
+    if not listed:
+        return record
+    code = [p for p in parts if not is_feature_ref(p)]
+    if not code:
+        raise LauncherPatternMissing(listed[0], "generator code beside the option list")
+    moved = {k: v for k, v in record.items() if k != "source_ref"}
+    return {**moved, "choices_from": ", ".join(listed), "source_ref": ", ".join(code)}