refactor: remove dead code — 1,784 lines across 77 files (#9180)

Deep scan with vulture, pyflakes, and manual cross-referencing identified:
- 41 dead functions/methods (zero callers in production)
- 7 production-dead functions (only test callers, tests deleted)
- 5 dead constants/variables
- ~35 unused imports across agent/, hermes_cli/, tools/, gateway/

Categories of dead code removed:
- Refactoring leftovers: _set_default_model, _setup_copilot_reasoning_selection,
  rebuild_lookups, clear_session_context, get_logs_dir, clear_session
- Unused API surface: search_models_dev, get_pricing, skills_categories,
  get_read_files_summary, clear_read_tracker, menu_labels, get_spinner_list
- Dead compatibility wrappers: schedule_cronjob, list_cronjobs, remove_cronjob
- Stale debug helpers: get_debug_session_info copies in 4 tool files
  (centralized version in debug_helpers.py already exists)
- Dead gateway methods: send_emote, send_notice (matrix), send_reaction
  (bluebubbles), _normalize_inbound_text (feishu), fetch_room_history
  (matrix), _start_typing_indicator (signal), parse_feishu_post_content
- Dead constants: NOUS_API_BASE_URL, SKILLS_TOOL_DESCRIPTION,
  FILE_TOOLS, VALID_ASPECT_RATIOS, MEMORY_DIR
- Unused UI code: _interactive_provider_selection,
  _interactive_model_selection (superseded by prompt_toolkit picker)

Test suite verified: 609 tests covering affected files all pass.
Tests for removed functions deleted. Tests using removed utilities
(clear_read_tracker, MEMORY_DIR) updated to use internal APIs directly.

tests/gateway/test_matrix.py

@@ -1831,45 +1831,4 @@ class TestMatrixPresence:
         assert result is False
 
 
-# ---------------------------------------------------------------------------
-# Emote & notice
-# ---------------------------------------------------------------------------
 
-class TestMatrixMessageTypes:
-    def setup_method(self):
-        self.adapter = _make_adapter()
-
-    @pytest.mark.asyncio
-    async def test_send_emote(self):
-        """send_emote should call send_message_event with m.emote."""
-        mock_client = MagicMock()
-        # mautrix returns EventID string directly
-        mock_client.send_message_event = AsyncMock(return_value="$emote1")
-        self.adapter._client = mock_client
-
-        result = await self.adapter.send_emote("!room:ex", "waves hello")
-        assert result.success is True
-        assert result.message_id == "$emote1"
-        call_args = mock_client.send_message_event.call_args
-        content = call_args.args[2] if len(call_args.args) > 2 else call_args.kwargs.get("content")
-        assert content["msgtype"] == "m.emote"
-
-    @pytest.mark.asyncio
-    async def test_send_notice(self):
-        """send_notice should call send_message_event with m.notice."""
-        mock_client = MagicMock()
-        mock_client.send_message_event = AsyncMock(return_value="$notice1")
-        self.adapter._client = mock_client
-
-        result = await self.adapter.send_notice("!room:ex", "System message")
-        assert result.success is True
-        assert result.message_id == "$notice1"
-        call_args = mock_client.send_message_event.call_args
-        content = call_args.args[2] if len(call_args.args) > 2 else call_args.kwargs.get("content")
-        assert content["msgtype"] == "m.notice"
-
-    @pytest.mark.asyncio
-    async def test_send_emote_empty_text(self):
-        self.adapter._client = MagicMock()
-        result = await self.adapter.send_emote("!room:ex", "")
-        assert result.success is False