refactor(gateway): migrate Slack adapter to bundled plugin

[teknium1]

Summary

Slack is now a bundled plugin (plugins/platforms/slack/) discovered via the platform registry instead of hardcoded Platform.SLACK touchpoints in core — the same shape as the Discord (#24356) and Home Assistant (#40709) migrations. Advances #41112 / #3823.

Changes

• Adapter relocated gateway/platforms/slack.py → plugins/platforms/slack/adapter.py (git rename, history preserved) + __init__.py / plugin.yaml.
• register(ctx) replaces the Platform.SLACK elif in gateway/run.py::_create_adapter().
• _standalone_send() replaces the legacy _send_slack() in tools/send_message_tool.py; deliver=slack cron delivery now flows through the registry's standalone_sender_fn. mrkdwn formatting moved into the plugin.
• _apply_yaml_config() owns the config.yaml slack: → SLACK_* env bridge (require_mention, strict_mention, allow_bots, free_response_channels, reactions, allowed_channels), replacing the hardcoded block in gateway/config.py.
• interactive_setup() replaces hermes_cli/setup.py::_setup_slack + the static _PLATFORMS["slack"] dict in hermes_cli/gateway.py; setup metadata is discovered dynamically.
• is_connected() probes SLACK_BOT_TOKEN; max_message_length=39000 on the PlatformEntry (registry fallback covers it — dropped the _MAX_LENGTHS entry).
• Env→PlatformConfig seeding and the _is_user_authorized allowlist maps stay in core (same as Discord/HA/Mattermost).

Bug fixed during migration

The registry-driven plugin-enable pass in _apply_env_overrides re-enabled any plugin platform whose is_connected() passed, ignoring an explicit enabled: false. Slack is the first plugin with an enabled-false-wins test, so it exposed this latent bug (Discord had no such test). Added an explicit-disable guard (_enabled_explicit + enabled=False → skip) and switched the slack env-block to read (not pop) the flag so the guard can see it; the flag is still cleared in the final per-platform cleanup.

Validation

	Result
Targeted suites (slack / config / setup / registry / send / media)	442 passing, 0 failing
test_explicit_{top_level,platforms}_slack_enabled_false_wins	restored (were broken by the migration, now green)
Live E2E (real plugin discovery → registry resolves SlackAdapter, env-only enable, standalone sender wired, YAML bridge, dynamic setup discovery)	18/18

Test imports rewritten across 11 files (gateway.platforms.slack → plugins.platforms.slack.adapter). The _setup_slack home-channel tests moved to tests/gateway/test_slack_plugin_setup.py (exercising interactive_setup); the slack-formatting tests in test_send_message_tool now patch the registry standalone_sender_fn and assert the mrkdwn text reaches the wire.

Infographic

[github-actions]

🔎 Lint report: hermes/hermes-87ac0a8e vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 10002 on HEAD, 10002 on base (➖ 0)

🆕 New issues (18):

Rule	Count
unresolved-import	5
invalid-method-override	4
invalid-assignment	3
invalid-return-type	2
unresolved-attribute	2
call-non-callable	1
invalid-raise	1

First entries

tools/send_message_tool.py:830: [invalid-assignment] invalid-assignment: Invalid subscript assignment with key of type `Literal["warnings"]` and value of type `list[str | Unknown]` on object of type `dict[str, str]`
plugins/platforms/slack/adapter.py:3414: [invalid-return-type] invalid-return-type: Function can implicitly return `None`, which is not assignable to return type `str`
plugins/platforms/slack/adapter.py:1709: [invalid-method-override] invalid-method-override: Invalid override of method `send_image_file`: Definition is incompatible with `BasePlatformAdapter.send_image_file`
plugins/platforms/slack/adapter.py:89: [unresolved-import] unresolved-import: Cannot resolve imported module `slack_bolt.async_app`
plugins/platforms/slack/adapter.py:832: [call-non-callable] call-non-callable: Object of type `<special-form 'typing.Any'>` is not callable
tests/tools/test_signal_media.py:186: [invalid-assignment] invalid-assignment: Object of type `((...) -> Awaitable[dict[Unknown, Unknown]]) | None` is not assignable to attribute `standalone_sender_fn` on type `PlatformEntry | None`
plugins/platforms/slack/adapter.py:3470: [invalid-return-type] invalid-return-type: Function can implicitly return `None`, which is not assignable to return type `bytes`
plugins/platforms/slack/adapter.py:3472: [unresolved-import] unresolved-import: Cannot resolve imported module `httpx`
plugins/platforms/slack/adapter.py:1891: [invalid-method-override] invalid-method-override: Invalid override of method `send_document`: Definition is incompatible with `BasePlatformAdapter.send_document`
tests/tools/test_signal_media.py:174: [invalid-assignment] invalid-assignment: Object of type `AsyncMock` is not assignable to attribute `standalone_sender_fn` on type `PlatformEntry | None`
plugins/platforms/slack/adapter.py:90: [unresolved-import] unresolved-import: Cannot resolve imported module `slack_bolt.adapter.socket_mode.async_handler`
tests/tools/test_signal_media.py:173: [unresolved-attribute] unresolved-attribute: Attribute `standalone_sender_fn` is not defined on `None` in union `PlatformEntry | None`
plugins/platforms/slack/adapter.py:1935: [invalid-raise] invalid-raise: Cannot raise object of type `None | Exception`: Not an instance or subclass of `BaseException`
plugins/platforms/slack/adapter.py:1833: [invalid-method-override] invalid-method-override: Invalid override of method `send_video`: Definition is incompatible with `BasePlatformAdapter.send_video`
plugins/platforms/slack/adapter.py:1135: [invalid-method-override] invalid-method-override: Invalid override of method `send_private_notice`: Definition is incompatible with `BasePlatformAdapter.send_private_notice`
plugins/platforms/slack/adapter.py:91: [unresolved-import] unresolved-import: Cannot resolve imported module `slack_sdk.web.async_client`
plugins/platforms/slack/adapter.py:3644: [unresolved-import] unresolved-import: Cannot resolve imported module `aiohttp`
plugins/platforms/slack/adapter.py:1055: [unresolved-attribute] unresolved-attribute: Attribute `client` is not defined on `None` in union `Any | None`

✅ Fixed issues (14):

Rule	Count
unresolved-import	5
invalid-method-override	4
invalid-return-type	2
call-non-callable	1
invalid-raise	1
unresolved-attribute	1

First entries

gateway/platforms/slack.py:1709: [invalid-method-override] invalid-method-override: Invalid override of method `send_image_file`: Definition is incompatible with `BasePlatformAdapter.send_image_file`
gateway/platforms/slack.py:89: [unresolved-import] unresolved-import: Cannot resolve imported module `slack_bolt.async_app`
gateway/platforms/slack.py:1891: [invalid-method-override] invalid-method-override: Invalid override of method `send_document`: Definition is incompatible with `BasePlatformAdapter.send_document`
gateway/platforms/slack.py:92: [unresolved-import] unresolved-import: Cannot resolve imported module `aiohttp`
gateway/platforms/slack.py:90: [unresolved-import] unresolved-import: Cannot resolve imported module `slack_bolt.adapter.socket_mode.async_handler`
gateway/platforms/slack.py:3470: [invalid-return-type] invalid-return-type: Function can implicitly return `None`, which is not assignable to return type `bytes`
gateway/platforms/slack.py:3414: [invalid-return-type] invalid-return-type: Function can implicitly return `None`, which is not assignable to return type `str`
gateway/platforms/slack.py:832: [call-non-callable] call-non-callable: Object of type `<special-form 'typing.Any'>` is not callable
gateway/platforms/slack.py:1833: [invalid-method-override] invalid-method-override: Invalid override of method `send_video`: Definition is incompatible with `BasePlatformAdapter.send_video`
gateway/platforms/slack.py:1135: [invalid-method-override] invalid-method-override: Invalid override of method `send_private_notice`: Definition is incompatible with `BasePlatformAdapter.send_private_notice`
gateway/platforms/slack.py:91: [unresolved-import] unresolved-import: Cannot resolve imported module `slack_sdk.web.async_client`
gateway/platforms/slack.py:3472: [unresolved-import] unresolved-import: Cannot resolve imported module `httpx`
gateway/platforms/slack.py:1935: [invalid-raise] invalid-raise: Cannot raise object of type `None | Exception`: Not an instance or subclass of `BaseException`
gateway/platforms/slack.py:1055: [unresolved-attribute] unresolved-attribute: Attribute `client` is not defined on `None` in union `Any | None`

Unchanged: 5176 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.

[teknium1]

Folded into #41284 — the slack migration commit was cherry-picked onto the combined all-platforms branch (authorship preserved in git log), so the entire gateway-channel → plugin transition lands as one PR per Teknium's request. Closing this in favor of #41284