fix(slack): handle bot alert Block Kit text

[Sungmin-agmo]

Summary

• Treat free_response_channels as an explicit opt-in for external Slack bot/app messages so alert channels can trigger the agent without requiring a mention.
• Extract readable text from Slack Block Kit section, header, fields, context, input, and actions blocks when top-level text is empty.
• Include attachment-level Block Kit blocks and attachment fields in inbound Slack message text, covering Grafana/Alertmanager-style alert payloads.
• Preserve self-bot loop prevention, allowed-channel gating, mention gating outside free-response channels, and existing rich-text quote extraction.

Why

Slack alert apps can emit bot_message events with empty top-level text while the human-visible payload is only present in blocks or attachments[].blocks. Those events were received by the Slack gateway but could be dropped before becoming inbound Hermes messages.

Tests

• python -m pytest tests/gateway/test_slack_mention.py — 66 passed, 2 warnings
• python -m pytest tests/gateway/test_slack*.py — 335 passed, 51 warnings (existing async mock/socket watchdog warnings)
• python -m compileall -q plugins/platforms/slack/adapter.py tests/gateway/test_slack_mention.py
• git diff --check

[Sungmin-agmo]

Closing: this PR was opened against the receiver side by mistake. The intended sender-side fix is now in AGMO-Inc/sdm-infra#356.

[Sungmin-agmo]

Reopening after producer-side validation: Slack/Grafana webhook now emits top-level text, but external Slack app events still stop at raw bot_message logs and do not reach gateway inbound handling unless receiver accepts bot messages in explicitly configured free-response alert channels.\n\nVerification rerun locally:\n- python -m pytest tests/gateway/test_slack_mention.py: 66 passed\n- python -m pytest tests/gateway/test_slack*.py: 335 passed\n- python -m compileall -q plugins/platforms/slack/adapter.py tests/gateway/test_slack_mention.py: passed

[teknium1]

Thanks for tracing the receiver-side Slack alert path. The live inbound premise is still present on current main: plugins/platforms/slack/adapter.py:2600-2610 rejects bot events before Block Kit/attachment extraction.

Problems

• The proposed free-response bypass is not end-to-end. Slack bot events are marked is_bot=True at plugins/platforms/slack/adapter.py:3171-3175, while gateway/authz_mixin.py:345-363 independently requires SLACK_ALLOW_BOTS=mentions or all. Thus a free-response alert channel alone is still denied after handle_message.
• PR commit a7ed068c256aa0cb7037532716b9548a18090361 tests the adapter with a stubbed handle_message, so it does not cover that authorization boundary.
• The same empty-text payload class remains in thread context at plugins/platforms/slack/adapter.py:3788-3790 and parent lookup at :3891-3894; the cross-referenced fix(slack): read thread context from message attachments and blocks #61261 covers that sibling case.

Suggested changes

• Define and test a single explicit admission rule shared by adapter routing and GatewayRunner authorization, preserving self-loop and allowed_channels guards.
• Reuse one Block Kit/attachment text helper for live messages and thread-context fetches.

Automated hermes-sweeper review.

[teknium1]

Closing as superseded by #69316 (merged): block extraction landed; the bundled free_response_channels behavior change is out of this bug-class scope — feel free to re-file it standalone.

Thanks for digging into this — the consolidated fix stands on the cluster's collective analysis, and your work is credited in #69316's summary.