Commands typed in Slack could be mangled by every enrichment layer the
adapter applies to normal messages:
- Block Kit / unfurl / attachment-notice / text-file injection could
prepend or append content around a command, moving the command token
away from character zero or polluting its arguments. Commands are now
restored from canonical authored input after all enrichment
(final is_command_text guard before MessageEvent construction).
- @bot /cmd (typed slash behind a mention) was never classified as a
command; the mention-strip branch now re-probes for both slash and
bang forms.
- The Slack Agent-view context label ([Slack app context: ...]) was
prepended to command events too; now command-exempt.
- Native slash payload arguments were strip()ed, destroying meaningful
spacing inside/after arguments; only the command delimiter is
nonsemantic now.
- Slash payload thread identity (thread_ts/message_ts, top-level or
nested in message/container) is preserved onto SessionSource so
session-scoped commands hit the same thread session.
- /queue and /steer queued fallbacks now propagate channel_context so a
command that triggered first-entry thread backfill doesn't lose the
history when re-queued.
Adapted from PR #66310 to the post-#69320 channel_context design (thread
history already rides MessageEvent.channel_context, never text).
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