feat: install files into retrobat emulator folders

RetroBat's Pico8 generator runs pico8.exe from AppConfig.GetFullPath:
the emulatorLauncher.cfg key, else the first existing of four folders of
the RetroBat install. The registry describes that search
(emulators_directory) and the manifest writes such a file as
root: emulators. The installer places it only when the BIOS folder sits
beside RetroBat's launcher config and the config does not move the
folder, and names it no_emulators_directory otherwise. Packs skip it as
they skip root: roms.

The PICO-8 0.2.7 Windows build (pico8.exe, SDL2.dll) is collected from
the archive.org copy of pico-8_0.2.7_windows.zip, its pico8.dat being
the 0.2.7 one already held.

scripts/cross_reference.py

@@ -24,6 +24,7 @@ from pathlib import Path
 
 sys.path.insert(0, os.path.dirname(__file__))
 from common import (
+    OUTER_ROOTS,
     platform_arg,
     ProfileSelectionError,
     _foreign_tree,
@@ -867,7 +868,7 @@ def _cross_reference_profile(
         # archive.
         # A platform declares files of its BIOS tree: none answers for one
         # the core reads below the save directory.
-        in_platform = not save_root and f.get("root") != "roms" and declaration_settles(
+        in_platform = not save_root and f.get("root") not in OUTER_ROOTS and declaration_settles(
             f, fname, platform_names, effective_path, index.get("folded_slots", frozenset()),
             index.get("declared_contents"),
         )
@@ -955,8 +956,8 @@ def _cross_reference_profile(
             entry["root"] = "save"
         elif f.get("unplaced"):
             entry["unplaced"] = f["unplaced"]
-        elif f.get("root") == "roms":
-            entry["root"] = "roms"
+        elif f.get("root") in OUTER_ROOTS:
+            entry["root"] = f["root"]
         elif index.get("launcher_candidates") is not None:
             # What verify hands the launcher layer for the same entry.
             probe = {