refactor: repoint 10 MessageEvent/MessageType importers that landed on main after the event.py split

Five test files and five evals scripts merged since this branch's base still import the
moved names via gateway.platforms.base. They work (base.py imports the names for its own
use) but the PR's invariant is that in-tree code imports from the defining module.

evals/delivery_flood_wire.py

@@ -95,7 +95,7 @@ async def setup(url):
 
 async def produce(runner, adapter, chat):
     from gateway.config import Platform
-    from gateway.platforms.base import MessageEvent
+    from gateway.platforms.event import MessageEvent
     from gateway.session import SessionSource
     source = SessionSource(platform=Platform.TELEGRAM, chat_id=chat, thread_id='77')
     entry = await runner.async_session_store.get_or_create_session(source)

evals/gateway_status_render/iteration_ceiling_ab.py

@@ -39,7 +39,8 @@ def _agent(max_iterations: int | None):
 
 async def _busy_ack(agent) -> str:
     import gateway.run as gr
-    from gateway.platforms.base import MessageEvent, MessageType, SessionSource, build_session_key
+    from gateway.platforms.base import SessionSource, build_session_key
+    from gateway.platforms.event import MessageEvent, MessageType
 
     gr._load_gateway_config = lambda: {"display": {"platforms": {"telegram": {"busy_ack_detail": True}}}}
     runner = object.__new__(gr.GatewayRunner)

evals/heartbeat_idle_wire.py

@@ -17,7 +17,8 @@ from unittest.mock import patch
 sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
 
 from gateway.config import GatewayConfig, Platform, PlatformConfig  # noqa: E402
-from gateway.platforms.base import BasePlatformAdapter, MessageEvent, SendResult  # noqa: E402
+from gateway.platforms.base import BasePlatformAdapter, SendResult  # noqa: E402
+from gateway.platforms.event import MessageEvent  # noqa: E402
 from gateway.run import GatewayRunner  # noqa: E402
 from gateway.session import SessionSource, SessionStore, build_session_key  # noqa: E402
 from hermes_cli import heartbeat  # noqa: E402

evals/postmortem/review_probes/goal_repaste_probe.py

@@ -35,7 +35,7 @@ from cli import HermesCLI
 from hermes_cli import cli_commands_mixin, goals
 from gateway.slash_commands_goals import GatewayGoalCommandsMixin
 from gateway.config import Platform
-from gateway.platforms.base import MessageEvent, MessageType
+from gateway.platforms.event import MessageEvent, MessageType
 from gateway.session import SessionSource
 from tui_gateway import server
 

evals/token_accounting/display_provenance.py

@@ -25,7 +25,7 @@ def child(out: Path) -> None:
     from gateway.config import GatewayConfig
     from gateway.session import SessionStore, SessionSource
     from gateway.config import Platform
-    from gateway.platforms.base import MessageEvent
+    from gateway.platforms.event import MessageEvent
 
     runner = GatewayRunner.__new__(GatewayRunner)
     runner.config = GatewayConfig()

tests/gateway/test_busy_steer_origin.py

@@ -5,7 +5,7 @@ import json
 import pytest
 
 from gateway.config import GatewayConfig, Platform
-from gateway.platforms.base import MessageEvent
+from gateway.platforms.event import MessageEvent
 from gateway.run import GatewayRunner
 from gateway.session import SessionSource
 

tests/gateway/test_heartbeat_poller.py

@@ -6,7 +6,8 @@ from types import SimpleNamespace
 import pytest
 
 from gateway.config import Platform, PlatformConfig
-from gateway.platforms.base import BasePlatformAdapter, MessageEvent, SendResult
+from gateway.platforms.base import BasePlatformAdapter, SendResult
+from gateway.platforms.event import MessageEvent
 from gateway.run import GatewayRunner
 from gateway.session import SessionSource, build_session_key
 from hermes_cli.heartbeat import HeartbeatManager

tests/gateway/test_reply_to_injection.py

@@ -63,7 +63,7 @@ async def test_reply_prefix_injected_when_text_absent_from_history():
 @pytest.mark.asyncio
 async def test_telegram_long_reply_reaches_prompt_without_losing_later_items():
     """The native reply already has the full message; preparation must not trim it."""
-    from gateway.platforms.base import MessageType
+    from gateway.platforms.event import MessageType
     from tests.gateway.test_telegram_reply_quote import _make_adapter, _make_message
 
     quoted = "\n".join(

tests/gateway/test_slack_model_picker.py

@@ -628,7 +628,7 @@ class TestSlackModelPickerGatewayIntegration:
 
         import yaml
 
-        from gateway.platforms.base import MessageEvent, MessageType
+        from gateway.platforms.event import MessageEvent, MessageType
         from gateway.session import SessionSource
 
         captured = {}
@@ -684,7 +684,7 @@ class TestSlackModelPickerGatewayIntegration:
     async def test_text_fallback_when_no_picker(self, tmp_path, monkeypatch):
         import yaml
 
-        from gateway.platforms.base import MessageEvent, MessageType
+        from gateway.platforms.event import MessageEvent, MessageType
         from gateway.session import SessionSource
 
         class SlackNoPickerAdapter:

tests/gateway/test_telegram_mention_context.py

@@ -7,7 +7,7 @@ from unittest.mock import AsyncMock
 
 import pytest
 
-from gateway.platforms.base import MessageType
+from gateway.platforms.event import MessageType
 from gateway.run import GatewayRunner
 from tests.gateway.test_telegram_group_gating import (
     _dm_message, _group_message, _group_voice_message, _make_adapter,