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  _interactive_model_selection (superseded by prompt_toolkit picker)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.

tools/transcription_tools.py

@@ -37,8 +37,6 @@ from utils import is_truthy_value
 from tools.managed_tool_gateway import resolve_managed_tool_gateway
 from tools.tool_backend_helpers import managed_nous_tools_enabled, resolve_openai_audio_api_key
 
-from hermes_constants import get_hermes_home
-
 logger = logging.getLogger(__name__)
 
 # ---------------------------------------------------------------------------
@@ -93,35 +91,6 @@ _local_model_name: Optional[str] = None
 # ---------------------------------------------------------------------------
 
 
-def get_stt_model_from_config() -> Optional[str]:
-    """Read the STT model name from ~/.hermes/config.yaml.
-
-    Provider-aware: reads from the correct provider-specific section
-    (``stt.local.model``, ``stt.openai.model``, etc.).  Falls back to
-    the legacy flat ``stt.model`` key only for cloud providers — if the
-    resolved provider is ``local`` the legacy key is ignored to prevent
-    OpenAI model names (e.g. ``whisper-1``) from being fed to
-    faster-whisper.
-
-    Silently returns ``None`` on any error (missing file, bad YAML, etc.).
-    """
-    try:
-        stt_cfg = _load_stt_config()
-        provider = stt_cfg.get("provider", DEFAULT_PROVIDER)
-        # Read from the provider-specific section first
-        provider_model = stt_cfg.get(provider, {}).get("model")
-        if provider_model:
-            return provider_model
-        # Legacy flat key — only honour for non-local providers to avoid
-        # feeding OpenAI model names (whisper-1) to faster-whisper.
-        if provider not in ("local", "local_command"):
-            legacy = stt_cfg.get("model")
-            if legacy:
-                return legacy
-    except Exception:
-        pass
-    return None
-
 
 def _load_stt_config() -> dict:
     """Load the ``stt`` section from user config, falling back to defaults."""