fix(slack): preserve thread context for proactive replies

Capture Slack thread metadata for cron and message-tool deliveries so replies stay in the originating thread, and hydrate first thread mentions with recent Slack context.

Made-with: Cursor

tests/cron/test_cron_tool_list.py

@@ -382,6 +382,21 @@ def test_add_job_empty_message_returns_actionable_error(tmp_path) -> None:
     assert "Retry including message=" in result
 
 
+def test_add_job_captures_metadata_and_session_key(tmp_path) -> None:
+    """CronTool stores channel metadata and session_key when adding a job."""
+    tool = _make_tool(tmp_path)
+    meta = {"slack": {"thread_ts": "111.222", "channel_type": "channel"}}
+    tool.set_context("slack", "C99", metadata=meta, session_key="slack:C99:111.222")
+
+    result = tool._add_job("test", "say hi", 60, None, None, None)
+    assert "Created job" in result
+
+    jobs = tool._cron.list_jobs()
+    assert len(jobs) == 1
+    assert jobs[0].payload.channel_meta == meta
+    assert jobs[0].payload.session_key == "slack:C99:111.222"
+
+
 def test_list_excludes_disabled_jobs(tmp_path) -> None:
     tool = _make_tool(tmp_path)
     job = tool._cron.add_job(