refactor: nuke gratuitous XML serialization + delete argument_parser

Argument parser:
- Delete ``strix/tools/argument_parser.py`` and its tests. The SDK
  validates and types tool arguments via Pydantic before they hit our
  wrappers, and the in-container tool server receives JSON-typed
  kwargs over the wire. The string-coercion belt-and-suspenders is no
  longer pulling its weight.

XML → JSON / typed structures:
- ``create_vulnerability_report``: ``cvss_breakdown`` is now a
  ``dict[str, str]`` of the 8 metrics; ``code_locations`` is a
  ``list[dict]``. No more XML parsing in the tool or the renderer.
- ``check_duplicate``: the dedup judge now emits a single JSON object
  instead of an ``<dedupe_result>`` block. Strict JSON parser handles
  optional code-fence wrappers.
- ``agent_finish``: completion report posted to the parent inbox is a
  JSON object (``kind``, ``from``, ``agent_id``, ``success``,
  ``summary``, ``findings``, ``recommendations``) rather than a
  hand-rolled ``<agent_completion_report>`` XML envelope.
- ``create_agent``: identity preamble + inherited-context markers are
  plain bracketed labels rather than ``<agent_delegation>`` /
  ``<inherited_context_from_parent>`` envelopes.
- ``inject_messages_filter``: peer messages get a
  ``[Message from agent <id> | type=... | priority=...]`` header line
  instead of an ``<inter_agent_message>`` envelope.
- Crash + system-warning messages: bracketed labels, no XML.
- System prompt: the inter-agent block now describes the new header
  format and drops the "never echo XML envelope" rule.
- ``strix/llm/utils.py``: deleted. ``clean_content`` collapsed into a
  one-line blank-line normalizer in the agent-message renderer (the
  XML envelope scrub had nothing left to scrub).

Tests updated to match the new shapes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

strix/runtime/tool_server.py

@@ -69,7 +69,6 @@ class ToolExecutionResponse(BaseModel):
 
 
 async def _run_tool(agent_id: str, tool_name: str, kwargs: dict[str, Any]) -> Any:
-    from strix.tools.argument_parser import convert_arguments
     from strix.tools.context import set_current_agent_id
     from strix.tools.registry import get_tool_by_name
 
@@ -79,8 +78,7 @@ async def _run_tool(agent_id: str, tool_name: str, kwargs: dict[str, Any]) -> An
     if not tool_func:
         raise ValueError(f"Tool '{tool_name}' not found")
 
-    converted_kwargs = convert_arguments(tool_func, kwargs)
-    return await asyncio.to_thread(tool_func, **converted_kwargs)
+    return await asyncio.to_thread(tool_func, **kwargs)
 
 
 @app.post("/execute", response_model=ToolExecutionResponse)