refactor(mcp): update ai_client.py 3 TOOL_NAMES sites (t1_5)

Phase 1 of any_type_componentization_20260621. Migrates ai_client.py:
- Line 560: new_tools = {name: False for name in mcp_client.TOOL_NAMES}
           -> mcp_tool_specs.tool_names()
- Line 582: _agent_tools = {name: True for name in mcp_client.TOOL_NAMES}
           -> mcp_tool_specs.tool_names()
- Line 1012: is_native = name in mcp_client.TOOL_NAMES
           -> name in mcp_tool_specs.tool_names()

Plus adds: from src import mcp_tool_specs

Verified:
  uv run pytest tests/test_mcp_tool_specs.py tests/test_mcp_client_beads.py tests/test_mcp_client_paths.py tests/test_audit_dataclass_coverage.py tests/test_type_aliases.py
    39 passed in 11.79s

No regressions. The mcp_client.TOOL_NAMES re-export is preserved for
backward compatibility with any external test/code that imports it.

src/ai_client.py

@@ -39,6 +39,7 @@ from typing      import Optional, Callable, Any, List, Union, cast, Iterable
 from src import project_manager
 from src import file_cache
 from src import mcp_client
+from src import mcp_tool_specs
 from src import mma_prompts
 from src import performance_monitor
 from src import project_manager
@@ -557,7 +558,7 @@ def _set_tool_preset_result(preset_name: Optional[str]) -> Result[None]:
   if preset_name in presets:
    preset = presets[preset_name]
    _active_tool_preset  = preset
-   new_tools            = {name: False for name in mcp_client.TOOL_NAMES}
+   new_tools            = {name: False for name in mcp_tool_specs.tool_names()}
    new_tools[TOOL_NAME] = False
    for cat in preset.categories.values():
     for tool in cat:
@@ -579,7 +580,7 @@ def set_tool_preset(preset_name: Optional[str]) -> None:
  _tool_approval_modes = {}
  if not preset_name or preset_name == "None":
   # Enable all tools if no preset
-  _agent_tools            = {name: True for name in mcp_client.TOOL_NAMES}
+  _agent_tools            = {name: True for name in mcp_tool_specs.tool_names()}
   _agent_tools[TOOL_NAME] = True
   _active_tool_preset     = None
  else:
@@ -1009,7 +1010,7 @@ async def _execute_single_tool_call_async(
    tool_executed = True
 
  if not tool_executed:
-  is_native   = name in mcp_client.TOOL_NAMES
+  is_native   = name in mcp_tool_specs.tool_names()
   ext_tools   = mcp_client.get_external_mcp_manager().get_all_tools()
   is_external = name in ext_tools
   if name and (is_native or is_external):