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  _interactive_model_selection (superseded by prompt_toolkit picker)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.

hermes_cli/commands.py

@@ -190,52 +190,6 @@ def resolve_command(name: str) -> CommandDef | None:
     return _COMMAND_LOOKUP.get(name.lower().lstrip("/"))
 
 
-def rebuild_lookups() -> None:
-    """Rebuild all derived lookup dicts from the current COMMAND_REGISTRY.
-
-    Called after plugin commands are registered so they appear in help,
-    autocomplete, gateway dispatch, Telegram menu, and Slack mapping.
-    """
-    global GATEWAY_KNOWN_COMMANDS
-
-    _COMMAND_LOOKUP.clear()
-    _COMMAND_LOOKUP.update(_build_command_lookup())
-
-    COMMANDS.clear()
-    for cmd in COMMAND_REGISTRY:
-        if not cmd.gateway_only:
-            COMMANDS[f"/{cmd.name}"] = _build_description(cmd)
-            for alias in cmd.aliases:
-                COMMANDS[f"/{alias}"] = f"{cmd.description} (alias for /{cmd.name})"
-
-    COMMANDS_BY_CATEGORY.clear()
-    for cmd in COMMAND_REGISTRY:
-        if not cmd.gateway_only:
-            cat = COMMANDS_BY_CATEGORY.setdefault(cmd.category, {})
-            cat[f"/{cmd.name}"] = COMMANDS[f"/{cmd.name}"]
-            for alias in cmd.aliases:
-                cat[f"/{alias}"] = COMMANDS[f"/{alias}"]
-
-    SUBCOMMANDS.clear()
-    for cmd in COMMAND_REGISTRY:
-        if cmd.subcommands:
-            SUBCOMMANDS[f"/{cmd.name}"] = list(cmd.subcommands)
-    for cmd in COMMAND_REGISTRY:
-        key = f"/{cmd.name}"
-        if key in SUBCOMMANDS or not cmd.args_hint:
-            continue
-        m = _PIPE_SUBS_RE.search(cmd.args_hint)
-        if m:
-            SUBCOMMANDS[key] = m.group(0).split("|")
-
-    GATEWAY_KNOWN_COMMANDS = frozenset(
-        name
-        for cmd in COMMAND_REGISTRY
-        if not cmd.cli_only or cmd.gateway_config_gate
-        for name in (cmd.name, *cmd.aliases)
-    )
-
-
 def _build_description(cmd: CommandDef) -> str:
     """Build a CLI-facing description string including usage hint."""
     if cmd.args_hint: