fix(slack): authorize bot/workflow senders before the no-user-id guard (salvage #52403)

[kshitijk4poor]

Summary

Salvage of #52403 by @cypctlinux (rebased onto current main with a conflict resolution). Lets allowed Slack bot/workflow senders route by authorizing them before the no-user-id guard.

The bug

gateway/authz_mixin.py has a {PLATFORM}_ALLOW_BOTS bypass, but on main it (a) didn't list Slack, and (b) ran the bot bypass ~83 lines after the if not user_id: return False guard. Slack Workflow-Builder / app posts arrive as subtype=bot_message with no user field → user_id=None, so they hit that guard and were rejected before the bypass could ever run. Net effect: SLACK_ALLOW_BOTS=mentions|all had no effect for exactly the workflow/app posts it was meant to admit.

The fix

• Relocate the platform_allow_bots_map + if getattr(source, "is_bot") bypass to run before the no-user-id guard (so a user=None bot event can still be admitted), and add Platform.SLACK: "SLACK_ALLOW_BOTS" to the map.
• Flag Slack bot-authored events as bot sources (is_bot = bool(event.get("bot_id")) or subtype == "bot_message") so the bypass applies.
• Regression tests: bot user_id=None authorized under mentions/all, denied when unset/none, humans unaffected.

The bypass still requires is_bot AND SLACK_ALLOW_BOTS ∈ {mentions, all}; unmapped platforms and non-bot traffic fall through to the guard exactly as before — moving it earlier changes when a would-be-authorized bot is admitted, never whether.

Rebase conflict resolution (this salvage)

main had drifted since the PR was cut: it added Platform.TELEGRAM: "TELEGRAM_ALLOW_BOTS" to the old (late-position) map. The PR's relocated map only had DISCORD/FEISHU/SLACK. Resolved by deleting the old block and re-adding Platform.TELEGRAM to the relocated map, so no platform is dropped — the map now has DISCORD/FEISHU/TELEGRAM/SLACK. Also added an AUTHOR_MAP entry (t.chen@aftership.com → @cypctlinux).

Chosen over competing PRs (issue: Slack bot mentions don't route)

This was a 5-PR cluster. #52403 is the correct base because it relocates the bypass before the guard — the actual user=None failure mode. Two near-duplicates are superseded:

• fix: route allowed Slack bot mentions #56286 (whitekid) adds the same map entry but leaves the bypass after the guard, so the headline workflow case stays dead-on-arrival (its test papers over this with a synthetic user_id).
• fix(slack): authorize app/webhook messages via SLACK_ALLOW_BOTS #40883 patches gateway/platforms/slack.py and gateway/run.py helpers that no longer exist on main (dead path).

Distinct/complementary PRs left open: #52390 (Block-Kit-only mention detection) and #51627 (peer bot-routing loops).

Review

Ran hermes-agent-dev + hermes-pr-review Phase 2c — 0 Critical / 0 Warnings. Verified the relocation opens no new hole, Telegram preserved, comment now literally accurate, consistent double-gate with the adapter's own bot filter. Locally: 53 tests pass (31 Slack bot-auth + 22 Telegram/Discord/Feishu bot-auth — the relocation doesn't regress other platforms).

Tests

pytest tests/gateway/test_slack_bot_auth_bypass.py tests/gateway/test_slack_approval_buttons.py -q   # 31 passed (CI runs the full suite)

Supersedes #52403 (and #56286 / #40883). Full credit to @cypctlinux.