Follow-up to the allowed_channels wildcard fix in the preceding commit.
The same '*' literal trap affected two other Discord channel config lists:
- DISCORD_IGNORED_CHANNELS: '*' was stored as the literal string in the
ignored set, and the intersection check never matched real channel IDs,
so '*' was a no-op instead of silencing every channel.
- DISCORD_FREE_RESPONSE_CHANNELS: same shape — '*' never matched, so
the bot still required a mention everywhere.
Add a '*' short-circuit to both checks, matching the allowed_channels
semantics. Extend tests/gateway/test_discord_allowed_channels.py with
regression coverage for all three lists.
Refs: #14920
allowed_channels: "*" in config (or DISCORD_ALLOWED_CHANNELS="*" env var)
is meant to allow all channels, but the check was comparing numeric channel
IDs against the literal string set {"*"} via set intersection — always empty,
so every message was silently dropped.
Add a "*" short-circuit before the set intersection, consistent with every
other platform's allowlist handling (Signal, Slack, Telegram all do this).
Fixes#14920
