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  _interactive_model_selection (superseded by prompt_toolkit picker)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/cronjob_tools.py

@@ -382,42 +382,6 @@ def cronjob(
         return tool_error(str(e), success=False)
 
 
-# ---------------------------------------------------------------------------
-# Compatibility wrappers
-# ---------------------------------------------------------------------------
-
-def schedule_cronjob(
-    prompt: str,
-    schedule: str,
-    name: Optional[str] = None,
-    repeat: Optional[int] = None,
-    deliver: Optional[str] = None,
-    model: Optional[str] = None,
-    provider: Optional[str] = None,
-    base_url: Optional[str] = None,
-    task_id: str = None,
-) -> str:
-    return cronjob(
-        action="create",
-        prompt=prompt,
-        schedule=schedule,
-        name=name,
-        repeat=repeat,
-        deliver=deliver,
-        model=model,
-        provider=provider,
-        base_url=base_url,
-        task_id=task_id,
-    )
-
-
-def list_cronjobs(include_disabled: bool = False, task_id: str = None) -> str:
-    return cronjob(action="list", include_disabled=include_disabled, task_id=task_id)
-
-
-def remove_cronjob(job_id: str, task_id: str = None) -> str:
-    return cronjob(action="remove", job_id=job_id, task_id=task_id)
-
 
 CRONJOB_SCHEMA = {
     "name": "cronjob",