Slack session keys include the workspace id since #70190, but the kanban
notifier rebuilds the wake source from a subscription row that has no scope
column, so every terminal-event wake keyed without the workspace.
The legacy-key adoption shipped in the same change (`_legacy_slack_session_key`,
`_recovered_row_matches_source_scope`) resolves that unscoped key onto the same
session_id, so the wake passes the busy guards that are keyed by routing key
(`_active_sessions`, `_running_agents`) and only collides afterwards, on session
id, under the per-session turn lease (#64934) — which serializes it behind the
live turn's flush. On a live Slack gateway that shows up as a duplicate run on
one task plus 400+s of waiting before the woken turn starts.
Same failure mode as #56580 / #72191 (chat_type), one field over, and it needs
no schema change: `_thread_metadata_for_source()` already stamps
`slack_team_id`, the notify subscription persists that dict as
`delivery_metadata`, and the notifier already unpacks it. Rows written by
`kanban_tools._maybe_auto_subscribe` carry no workspace, so fall back to the
adapter's channel → workspace map via `scope_id_for_chat()`, read with getattr
so adapters opt in and unscoped platforms' keys stay byte-identical. Slack
answers it from `_remember_channel_team`, which drops channels claimed by two
workspaces, so an unknown or ambiguous channel degrades to today's behavior
instead of guessing wrong.
Also adds the contributor email mapping the attribution check requires.
Co-authored-by: Junie <junie@jetbrains.com>