Post announcer and manager-stats reports via communication adapters

The last two Slack-hardwired automation reporters now reach Teams and
Telegram destinations. Slack destinations keep the existing
SlackNotifier + Block Kit path byte-identical; non-Slack destinations
post through getCommunicationProviderAdapter with the summary degraded
from Slack mrkdwn to standard markdown (new degradeSlackMrkdwnToMarkdown
helper), the settings-link footer becoming a cross-surface url button,
detail messages threaded under the root, and tracked automation threads
upserted with the destination surface.

Deployment eligibility generalizes like the triage runner: Slack
installations first, otherwise any connected communication provider
(manager-stats resolves its GitHub actor from the installation row on
Slack-less deployments). Registry declarations flip to
slack/teams/telegram for both.

ci_failure_triage and the suggester's advanced routing intentionally
stay Slack-only.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: daniel-lxs