feat(cli,gateway): /new accepts optional session name argument

Allow users to start a fresh session and immediately set its title by
passing a name to /new (or /reset):

    /new Refactor auth module

Changes:
- hermes_cli/commands.py: add args_hint='[name]' to /new command
- cli.py: parse title argument in process_command(), pass to new_session()
- cli.py: new_session() accepts title=None, sets title via SessionDB
- gateway/run.py: _handle_reset_command() parses title, sets on new entry
- gateway/session.py: reset_session() accepts optional display_name
- tests: add test_new_session_with_title, test_reset_command_with_title,
  test_new_command_in_help_output

All 36 affected tests pass.

tests/gateway/test_title_command.py

@@ -5,11 +5,12 @@ across all gateway messenger platforms.
 """
 
 import os
-from unittest.mock import MagicMock, patch
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 
-from gateway.config import Platform
+from gateway.config import GatewayConfig, Platform, PlatformConfig
 from gateway.platforms.base import MessageEvent
 from gateway.session import SessionSource
 
@@ -206,3 +207,87 @@ class TestTitleInHelp:
         import inspect
         source = inspect.getsource(GatewayRunner._handle_message)
         assert '"title"' in source
+
+
+# ---------------------------------------------------------------------------
+# /new with title
+# ---------------------------------------------------------------------------
+
+
+class TestResetCommandWithTitle:
+    """Tests for GatewayRunner._handle_reset_command with a title argument."""
+
+    @pytest.mark.asyncio
+    async def test_reset_command_with_title(self):
+        """Sending /new <title> resets session and sets the title."""
+        from datetime import datetime
+
+        from gateway.run import GatewayRunner
+        from gateway.session import SessionEntry, SessionSource, build_session_key
+
+        runner = object.__new__(GatewayRunner)
+        runner.config = GatewayConfig(
+            platforms={Platform.TELEGRAM: PlatformConfig(enabled=True, token="***")}
+        )
+        adapter = MagicMock()
+        adapter.send = AsyncMock()
+        runner.adapters = {Platform.TELEGRAM: adapter}
+        runner._voice_mode = {}
+        runner.hooks = SimpleNamespace(emit=AsyncMock(), loaded_hooks=False)
+        runner._session_model_overrides = {}
+        runner._pending_model_notes = {}
+        runner._background_tasks = set()
+
+        source = SessionSource(
+            platform=Platform.TELEGRAM,
+            user_id="12345",
+            chat_id="67890",
+            user_name="testuser",
+        )
+        session_key = build_session_key(source)
+        new_session_entry = SessionEntry(
+            session_key=session_key,
+            session_id="sess-new",
+            created_at=datetime.now(),
+            updated_at=datetime.now(),
+            platform=Platform.TELEGRAM,
+            chat_type="dm",
+        )
+        runner.session_store = MagicMock()
+        runner.session_store.get_or_create_session.return_value = new_session_entry
+        runner.session_store.reset_session.return_value = new_session_entry
+        runner.session_store._entries = {session_key: new_session_entry}
+        runner.session_store._generate_session_key.return_value = session_key
+        runner._running_agents = {}
+        runner._pending_messages = {}
+        runner._pending_approvals = {}
+        runner._session_db = MagicMock()
+        runner._agent_cache = {}
+        runner._agent_cache_lock = None
+        runner._is_user_authorized = lambda _source: True
+        runner._format_session_info = lambda: ""
+
+        event = _make_event(text="/new Custom Name")
+        result = await runner._handle_reset_command(event)
+
+        runner.session_store.reset_session.assert_called_once()
+        runner._session_db.set_session_title.assert_called_once_with(
+            "sess-new", "Custom Name"
+        )
+
+
+# ---------------------------------------------------------------------------
+# /new in help output
+# ---------------------------------------------------------------------------
+
+
+class TestNewInHelp:
+    """Verify /new appears in help text with the [name] args hint."""
+
+    def test_new_command_in_help_output(self):
+        """The gateway help output includes /new with the [name] hint."""
+        from hermes_cli.commands import gateway_help_lines
+        lines = gateway_help_lines()
+        new_line = next((line for line in lines if line.startswith("`/new ")), None)
+        assert new_line is not None
+        assert "[name]" in new_line