fix: preserve thread context for cronjob deliver=origin

When a cronjob is created from within a Telegram or Slack thread,
deliver=origin was posting to the parent channel instead of the thread.

Root cause: the gateway never set HERMES_SESSION_THREAD_ID in the
session environment, so cronjob_tools.py could not capture thread_id
into the job's origin metadata — even though the scheduler already
reads origin.get('thread_id').

Fix:
- gateway/run.py: set HERMES_SESSION_THREAD_ID when thread_id is
  present on the session context, and clear it in _clear_session_env
- tools/cronjob_tools.py: read HERMES_SESSION_THREAD_ID into origin

Closes #1219

tests/gateway/test_session_env.py

@@ -0,0 +1,45 @@
+import os
+
+from gateway.config import Platform
+from gateway.run import GatewayRunner
+from gateway.session import SessionContext, SessionSource
+
+
+def test_set_session_env_includes_thread_id(monkeypatch):
+    runner = object.__new__(GatewayRunner)
+    source = SessionSource(
+        platform=Platform.TELEGRAM,
+        chat_id="-1001",
+        chat_name="Group",
+        chat_type="group",
+        thread_id="17585",
+    )
+    context = SessionContext(source=source, connected_platforms=[], home_channels={})
+
+    monkeypatch.delenv("HERMES_SESSION_PLATFORM", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_CHAT_ID", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_CHAT_NAME", raising=False)
+    monkeypatch.delenv("HERMES_SESSION_THREAD_ID", raising=False)
+
+    runner._set_session_env(context)
+
+    assert os.getenv("HERMES_SESSION_PLATFORM") == "telegram"
+    assert os.getenv("HERMES_SESSION_CHAT_ID") == "-1001"
+    assert os.getenv("HERMES_SESSION_CHAT_NAME") == "Group"
+    assert os.getenv("HERMES_SESSION_THREAD_ID") == "17585"
+
+
+def test_clear_session_env_removes_thread_id(monkeypatch):
+    runner = object.__new__(GatewayRunner)
+
+    monkeypatch.setenv("HERMES_SESSION_PLATFORM", "telegram")
+    monkeypatch.setenv("HERMES_SESSION_CHAT_ID", "-1001")
+    monkeypatch.setenv("HERMES_SESSION_CHAT_NAME", "Group")
+    monkeypatch.setenv("HERMES_SESSION_THREAD_ID", "17585")
+
+    runner._clear_session_env()
+
+    assert os.getenv("HERMES_SESSION_PLATFORM") is None
+    assert os.getenv("HERMES_SESSION_CHAT_ID") is None
+    assert os.getenv("HERMES_SESSION_CHAT_NAME") is None
+    assert os.getenv("HERMES_SESSION_THREAD_ID") is None