fix: hold the pcem upstream pin at its last sync

upstream_commit 25b54e3f was dev's HEAD at the 2026-10-23 bump. dev has
been rewritten since, and the pin is on no branch (diverged 109/114), so
profile_sync reports it orphaned. libretro-pcem shares no history with
sarah-walker-pcem/pcem: it took mainline patches by hand until 2016-04-13
(c9f3593f, 223f434f). Its sound_adlibgold.c holds 10739b96, the last
upstream commit before that date, and the port has none of the 6x86 work
of 2016-04-27. The pin is held there with upstream_frozen.

emulators/pcem.yml

@@ -5,7 +5,8 @@ source: "https://github.com/libretro/libretro-pcem"
 upstream: "https://github.com/sarah-walker-pcem/pcem"
 profiled_date: "2026-03-24"
 source_commit: "e07923e902dcedcf65a502fb3f14e75b9ded5271"
-upstream_commit: "25b54e3ff1d51cbf2469b447e55bce7a589697e9"
+upstream_commit: "10739b9618e388a5bf8c21e752f12b3952fa83e1"
+upstream_frozen: "The port took PCem mainline patches by hand until 2016-04-13 (libretro-pcem c9f3593f, 223f434f), which carry this commit of 2016-04-12 and none after it."
 core_version: "v10.1"
 version_basis:
   kind: file

tests/test_audit_regressions.py

@@ -5800,6 +5800,19 @@ class XeniosFollowsThePreviewBranch(unittest.TestCase):
         self.assertNotIn("from the xenios branch", profile.get("notes", ""))
 
 
+class PcemUpstreamPinIsTheLastSync(unittest.TestCase):
+    """The pcem bump set upstream_commit to dev's HEAD 25b54e3f, and dev was
+    rewritten: the pin left every branch (compare: diverged 109/114). The
+    port shares no history with upstream and took mainline patches by hand
+    until 2016-04-13, whose last upstream commit is 10739b96. Held there, a
+    bump cannot move it to a HEAD the port never contained."""
+
+    def test_the_upstream_pin_is_held_at_the_last_sync(self):
+        profile = yaml.safe_load((ROOT / "emulators" / "pcem.yml").read_text(encoding="utf-8"))
+        self.assertEqual(profile["upstream_commit"], "10739b9618e388a5bf8c21e752f12b3952fa83e1")
+        self.assertTrue(profile.get("upstream_frozen"))
+
+
 class AHashScanLabelNamesNoOtherDump(unittest.TestCase):
     """A core that finds its firmware by content names no file, so each
     entry name is a label. ares labelled its Famicom Disk System revision