[Fix] Suggested tasks do not launch from Fast automation reports

[roomote-roomote]

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

What changed

Fast automation closeouts can now attach structured suggested tasks on Slack and Discord. The report delivery path persists ordinary suggestion work items, posts tracked suggestion cards beneath the report, adds reaction-launch instructions only when cards exist, and routes accepted suggestions through the existing task router.

The Fast reply contract rejects structured suggestions outside supported automation closeouts. Persistence and provider delivery are idempotent across retries, including concurrent occurrence delivery and Discord reports without an editable root message.

Fast and standard suggestions now share the identical registry contract: surface-scoped card-presence checks, conflict-safe tracked_messages registration, dedupe-key construction, and Slack reaction-fallback metadata. Standard current-thread Slack, Discord, Telegram, and Teams delivery all use the same registry helper as Fast, while scheduled Slack can inject its existing transaction executor.

Why this change was made

Fast automations previously had only a text-and-image reply contract. Although their prompts could ask for launchable follow-ups, Fast updated an ordinary report message without creating work_items or tracked_messages, leaving the existing thumbs-up reaction handlers with nothing to claim or launch. The initial fix duplicated standard card-registry and Slack metadata mechanics, so this revision centralizes those exact wire and persistence contracts to prevent drift.

Impact

Suggested tasks emitted by Fast automation reports are now real, reaction-launchable artifacts rather than inline promises. Slack and Discord reuse the established claim, account-mapping, routing, and task-launch lifecycle; unsupported surfaces keep follow-ups as ordinary report text without promising reaction-triggered execution.

Only behaviorally identical infrastructure is shared. Fast keeps event-scoped fingerprints, nullable source-task ownership, minimal title/brief validation, quoted card formatting, strict delivery failures, and router-only launch metadata. Standard suggestions keep source-task and repository-aware persistence, richer semantic validation, provider-specific formatting, root/summary lifecycle, best-effort delivery behavior, and their existing router-or-pinned routing choice.

[roomote-community]

No code issues found. See task

_{Reviewed dafdcbc}