[Fix] Suggested tasks leave the automation Slack thread when accepted

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Persist the canonical origin Session on task-backed Slack suggestion cards.
• Require scheduled suggestion publication to bind that Session to the exact Slack report thread before reporting success.
• Make binding failures retriable: the committed automation-thread receipt and tracked cards are reused on retry, so Slack messages are not duplicated even if the configured destination changes.
• Verify at acceptance that the persisted card origin routes the announcement and Fast launch through the original Session and Slack thread without depending on a source-task lookup.

Why this change was made

A scheduled automation could successfully publish suggestion cards even when its post-publication Session-to-Slack binding failed. Accepting one of those cards then kept the work in the automation Session but seeded a new Slack root because the Session had no usable Slack reply target.

The precise trigger for the observed missing binding was not confirmed, so this fixes the unsafe success state rather than assuming a specific historical failure.

Impact

New task-backed automation suggestions retain canonical Session provenance on the card and cannot complete publication without a matching Slack thread binding. Transient binding failures can be retried idempotently against the already-posted report. Existing historical cards are not backfilled, and Slack delivery remains outside the database transaction.

[roomote-community]

No code issues found. See task

_{Reviewed 4f29d23}