fix: pass the installer's own lint gate

install.py held a local it never read and, since the registry path
rules, a loop variable shadowing the platform module, so the py38
ruff gate the installer is held to failed. Both are fixed, and the
suite reads the two rules from the syntax tree since CI has no ruff.

install.py

@@ -175,7 +175,6 @@ def _os_default_dests(os_type: str) -> dict[str, Path]:
     home = Path.home()
     if os_type == "windows":
         profile = Path(os.environ.get("USERPROFILE", str(home)))
-        appdata = Path(os.environ.get("APPDATA", str(home / "AppData" / "Roaming")))
         return {
             # RetroArch's system directory defaults to <exe folder>\system
             # (platform_win32.c), and its installer to C:\RetroArch-Win64.
@@ -904,11 +903,11 @@ def _rule_path(template: str) -> Path:
 def _detect_by_path(os_type: str, found: list[tuple[str, Path]]) -> None:
     """Add what a registry path rule finds, for a platform not found yet."""
     systems = ("linux", "windows") if os_type == "wsl" else (os_type,)
-    for rule_os, platform, path, bios in _PATH_RULES:
-        if rule_os not in systems or any(name == platform for name, _ in found):
+    for rule_os, platform_name, path, bios in _PATH_RULES:
+        if rule_os not in systems or any(name == platform_name for name, _ in found):
             continue
         if _rule_path(path).exists():
-            found.append((platform, _rule_path(bios or path)))
+            found.append((platform_name, _rule_path(bios or path)))
 
 
 def detect_platforms(os_type: str) -> list[tuple[str, Path]]: