Review finding on #90154: only the wildcard ("*") branch of
_iter_missed_message_backfill_candidates skipped obfuscated channels. A
channel the bot previously talked in that later lost VIEW_CHANNEL still
entered the explicit-id branch and produced a failing history read on
every startup. Apply the predicate once, after both branches build the
candidate list, and import it at module level like the other helpers.
(During the rebase the predicate was also tightened, resolved in the original
commit: is_discord_channel_obfuscated catches AttributeError (the precise
expected failure) instead of a bare Exception so a genuine attribute bug
is not hidden behind the name fallback, and its docstring states the
deliberate bias of the sentinel-name fallback (a visible channel literally
named ___hidden___ is also skipped on discord.py builds without the flag).)
624777617c