refactor: nuke legacy harness, drop sdk_ prefixes

The SDK harness is the only path now; legacy host-side code is gone.
File names no longer carry the ``sdk_`` distinction.

Deleted legacy host-side modules:
- strix/agents/StrixAgent/ (template moved to strix/agents/prompts/)
- strix/agents/base_agent.py, state.py
- strix/llm/llm.py, config.py
- strix/runtime/docker_runtime.py, runtime.py
- strix/tools/executor.py, agents_graph/agents_graph_actions.py
- strix/interface/sdk_dispatch.py + the env-flag dispatch in cli.py

Renamed (drop ``sdk_`` prefix):
- strix/sdk_entry.py → strix/entry.py
- strix/agents/sdk_factory.py → strix/agents/factory.py
- strix/agents/sdk_prompt.py → strix/agents/prompt.py
- strix/tools/<x>/<x>_sdk_tool[s].py → strix/tools/<x>/tool[s].py
- strix/tools/_legacy_adapter.py → strix/tools/_state_adapter.py
- ``_legacy`` aliases inside the wrappers → ``_impl``

CLI + TUI now call ``run_strix_scan`` directly — they build the
sandbox image / sources_path locally and rely on
``session_manager.cleanup`` (called inside ``run_strix_scan``'s finally)
for teardown. Three TUI handlers that reached into legacy multi-agent
globals (``_agent_instances``, ``send_user_message_to_agent``,
``stop_agent``) are now no-ops with a TODO; reconnecting them to the
``AgentMessageBus`` is a follow-up.

Tracer.get_total_llm_stats no longer reaches into the deleted
``agents_graph_actions`` globals — the orchestration hooks now feed the
tracer via ``Tracer.record_llm_usage`` (live + completed buckets).
finish_scan's ``_check_active_agents`` and load_skill's runtime
``_agent_instances`` reach-in are no-op stubs; the
``AgentMessageBus`` is the source of truth post-migration.

llm/utils.py rewritten to keep only the streaming-parser helpers
(``normalize_tool_format``, ``parse_tool_invocations``,
``fix_incomplete_tool_call``, ``format_tool_call``, ``clean_content``).
``STRIX_MODEL_MAP`` moved to ``llm/multi_provider_setup.py`` (its only
remaining caller).

Per-file ruff ignores added for legacy interface modules (TUI / main /
CLI / utils / streaming_parser / tool_components) and tracer.py —
pre-existing PLC0415/BLE001/PLR0915 patterns are out of scope.

Tests: 287/287 passing. Renamed test files to drop ``sdk_`` prefix.
``test_tracer.py::test_get_total_llm_stats_aggregates_live_and_completed``
rewritten to feed ``Tracer.record_llm_usage`` instead of legacy globals.
Test file annotations added so pre-commit's strict mypy passes.

strix/tools/notes/tools.py

@@ -17,7 +17,7 @@ from typing import Any
 from agents import RunContextWrapper
 
 from strix.tools._decorator import strix_tool
-from strix.tools.notes import notes_actions as _legacy
+from strix.tools.notes import notes_actions as _impl
 
 
 def _dump(result: dict[str, Any]) -> str:
@@ -48,7 +48,7 @@ async def create_note(
     # Wrap in to_thread so we don't block the event loop while waiting
     # on the lock or fsync.
     result = await asyncio.to_thread(
-        _legacy.create_note,
+        _impl.create_note,
         title=title,
         content=content,
         category=category,
@@ -75,7 +75,7 @@ async def list_notes(
             when True, full content is included.
     """
     result = await asyncio.to_thread(
-        _legacy.list_notes,
+        _impl.list_notes,
         category=category,
         tags=tags,
         search=search,
@@ -87,7 +87,7 @@ async def list_notes(
 @strix_tool(timeout=30)
 async def get_note(ctx: RunContextWrapper, note_id: str) -> str:
     """Fetch one note by its 5-char ID. Returns full content."""
-    result = await asyncio.to_thread(_legacy.get_note, note_id=note_id)
+    result = await asyncio.to_thread(_impl.get_note, note_id=note_id)
     return _dump(result)
 
 
@@ -101,7 +101,7 @@ async def update_note(
 ) -> str:
     """Update a note's title, content, or tags. Pass ``None`` to leave a field unchanged."""
     result = await asyncio.to_thread(
-        _legacy.update_note,
+        _impl.update_note,
         note_id=note_id,
         title=title,
         content=content,
@@ -113,5 +113,5 @@ async def update_note(
 @strix_tool(timeout=30)
 async def delete_note(ctx: RunContextWrapper, note_id: str) -> str:
     """Delete a note. For wiki notes, also removes the rendered Markdown file."""
-    result = await asyncio.to_thread(_legacy.delete_note, note_id=note_id)
+    result = await asyncio.to_thread(_impl.delete_note, note_id=note_id)
     return _dump(result)