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  _interactive_model_selection (superseded by prompt_toolkit picker)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.

cli.py

@@ -4474,53 +4474,6 @@ class HermesCLI:
             _ask()
         return result[0]
 
-    def _interactive_provider_selection(
-        self, providers: list, current_model: str, current_provider: str
-    ) -> str | None:
-        """Show provider picker, return slug or None on cancel."""
-        choices = []
-        for p in providers:
-            count = p.get("total_models", len(p.get("models", [])))
-            label = f"{p['name']} ({count} model{'s' if count != 1 else ''})"
-            if p.get("is_current"):
-                label += "  ← current"
-            choices.append(label)
-
-        default_idx = next(
-            (i for i, p in enumerate(providers) if p.get("is_current")), 0
-        )
-
-        idx = self._run_curses_picker(
-            f"Select a provider (current: {current_model} on {current_provider}):",
-            choices,
-            default_index=default_idx,
-        )
-        if idx is None:
-            return None
-        return providers[idx]["slug"]
-
-    def _interactive_model_selection(
-        self, model_list: list, provider_data: dict
-    ) -> str | None:
-        """Show model picker for a given provider, return model_id or None on cancel."""
-        pname = provider_data.get("name", provider_data.get("slug", ""))
-        total = provider_data.get("total_models", len(model_list))
-
-        if not model_list:
-            _cprint(f"\n  No models listed for {pname}.")
-            return self._prompt_text_input("  Enter model name manually (or Enter to cancel): ")
-
-        choices = list(model_list) + ["Enter custom model name"]
-        idx = self._run_curses_picker(
-            f"Select model from {pname} ({len(model_list)} of {total}):",
-            choices,
-        )
-        if idx is None:
-            return None
-        if idx < len(model_list):
-            return model_list[idx]
-        return self._prompt_text_input("  Enter model name: ")
-
     def _open_model_picker(self, providers: list, current_model: str, current_provider: str, user_provs=None, custom_provs=None) -> None:
         """Open prompt_toolkit-native /model picker modal."""
         self._capture_modal_input_snapshot()