fix(plex): plain text survives a decimal reference too long to parse

int() refuses a decimal run past 4300 digits, so one such reference in a summary raised out of the sync and the text migration. Any number past seven significant digits is beyond U+10FFFF, so it becomes U+FFFD like any out-of-range reference; leading zeros are dropped first. The rails test's comment now says what it guards: both rails agree with the rollup.

backend/app/plex/plaintext.py

@@ -27,7 +27,14 @@ _REF = re.compile(r"&(?:#[0-9]+|#[xX][0-9a-fA-F]+|[A-Za-z][A-Za-z0-9]*);")
 
 def _decode(m: re.Match[str]) -> str:
     ref = m.group()
-    return html.unescape(ref) if ref[1] == "#" or ref[1:] in html5 else ref
+    if ref[1] != "#":
+        return html.unescape(ref) if ref[1:] in html5 else ref
+    if ref[2] in "xX":
+        return html.unescape(ref)
+    # `int()` refuses a decimal run past 4300 digits, and any number past seven significant digits is
+    # beyond U+10FFFF, which the parser turns into U+FFFD anyway.
+    digits = ref[2:-1].lstrip("0") or "0"
+    return "�" if len(digits) > 7 else html.unescape(f"&#{digits};")
 
 
 def plain_text(value: str | None) -> str | None:

backend/tests/test_plex_discover.py

@@ -168,8 +168,8 @@ def test_continue_watching_movies_and_shows(db, monkeypatch, override_dep):
 def test_a_continue_watching_show_says_whether_it_has_an_episode_to_resume(
     db, monkeypatch, override_dep
 ):
-    # Both in-progress rails (Discover's and Home's) take a show's card state from the one rollup:
-    # a show part watched with nothing to resume offers Play alone, not Continue + Restart.
+    # Both in-progress rails (Discover's and Home's) agree with the one rollup: a show part watched
+    # with nothing to resume offers Play alone, not Continue + Restart.
     from app.discover.queries import plex_in_progress
 
     user = _seed(db)

backend/tests/test_plex_plaintext.py

@@ -36,6 +36,9 @@ HU_SUMMARY = "<p>A műsorban minden p&aacute;rosnak stoppal kell eljutnia.</p>"
         # ...and only a whole entity name: a legacy one at its start ("&not", "&amp") is not.
         ("AT&notice; and &ampx;", "AT&notice; and &ampx;"),
         ("&#233;t&#xE9; &copy;", "été ©"),
+        # A decimal reference too long for int() to parse is out of range, like &#x110000;.
+        ("a &#" + "9" * 5000 + "; b", "a � b"),
+        ("&#" + "0" * 5000 + "65;", "A"),
         ("Plain summary.", "Plain summary."),
         ("  padded  ", "padded"),
         ("<p></p>", None),