fix: read pcsx_rearmed us slot as the default

CheckCdrom sets PSX_REGION_US before it reads the licence, and only
"Inc." or "Euro pe" move it (libpcsxcore/misc.c:422-453). A Latin
American disc boots the US slot, so its four BIOS images carry
latin-america and --region br,jp keeps them.

emulators/pcsx_rearmed.yml

@@ -36,13 +36,13 @@ files:
 
   - name: "scph5501.bin"
     description: "SCPH-5501 (v3.0 11-18-96 A)"
-    region: [north-america]
+    region: [north-america, latin-america]
     size: 524288
     required: false
     hle_fallback: true
     validation: [size]
     source_ref: "source frontend/libretro.c:3864-3867 (listed_bios[1])"
-    note: "Preferred US BIOS, searched first by exact filename."
+    note: "Preferred US BIOS, searched first by exact filename. The US slot is the detector's default: a disc takes it for both America licence strings and for any licence that is neither \"Inc.\" (JP) nor \"Euro pe\" (EU), and content without a disc boots it too (libpcsxcore/misc.c:422-453, frontend/libretro.c:2167-2171)."
 
   # -- Region: Europe (PSX_REGION_EU = 2) --
 
@@ -70,7 +70,7 @@ files:
 
   - name: "scph101.bin"
     description: "SCPH-101 (v4.4 03-24-00 A) - PSone US"
-    region: [north-america]
+    region: [north-america, latin-america]
     size: 524288
     required: false
     hle_fallback: true
@@ -80,7 +80,7 @@ files:
 
   - name: "scph7001.bin"
     description: "SCPH-7001 (v4.1 12-16-97 A)"
-    region: [north-america]
+    region: [north-america, latin-america]
     size: 524288
     required: false
     hle_fallback: true
@@ -89,7 +89,7 @@ files:
 
   - name: "scph1001.bin"
     description: "SCPH-1001 (v2.2 12-04-95 A)"
-    region: [north-america]
+    region: [north-america, latin-america]
     size: 524288
     required: false
     hle_fallback: true

tests/test_region.py

@@ -889,6 +889,8 @@ class RegionalRequestsKeepWhatTheCodeLoads(unittest.TestCase):
         ("ace-dl", ["france"], "private/firmware/Amstrad_s4.cpr"),
         ("duckstation", ["brazil"], "scph5501.bin"),
         ("duckstation", ["south-korea"], "scph5500.bin"),
+        ("pcsx_rearmed", ["brazil", "japan"], "scph5501.bin"),
+        ("pcsx_rearmed", ["brazil", "japan"], "scph1001.bin"),
         ("blastem", ["australia", "north-america"], "bios_CD_E.bin"),
         ("kega-fusion", ["australia", "north-america"], "eu_mcd1_9210.bin"),
     )
@@ -1118,6 +1120,24 @@ class MegaCdEuropeServesOceania(unittest.TestCase):
         self.assertEqual(narrow, [])
 
 
+class PcsxRearmedUsSlotIsTheDefault(unittest.TestCase):
+    """CheckCdrom sets PSX_REGION_US before reading the licence and only
+    "Inc." or "Euro pe" move it (libpcsxcore/misc.c:422-453): a disc of any
+    other market boots the US slot."""
+
+    def test_every_us_slot_bios_includes_latin_america(self):
+        from common import load_emulator_profiles
+
+        tagged = [
+            f for f in load_emulator_profiles("emulators")["pcsx_rearmed"]["files"]
+            if "north-america" in (f.get("region") or [])
+        ]
+        self.assertEqual(len(tagged), 4)
+        for entry in tagged:
+            with self.subTest(name=entry["name"]):
+                self.assertIn("latin-america", entry["region"])
+
+
 class FusionSmsExportBiosFollowsTheSetting(unittest.TestCase):
     """Kega Fusion tells a Japanese Master System cart from an export one by
     the header, then picks USA or EUR from its CountryOrder setting or a CRC32