fix(server): stop stacking a tool profile's visibility on every session

What the first Linux CI run of the 1.6 tree found.

- fastmcp 3's enable()/disable() append a Visibility transform per call,
  and a tool lookup walks the transform stack as nested calls. The
  lifespan re-applies the tool profile on every client connection, so an
  in-process server grew two layers per session until every tool call,
  system_status included, raised RecursionError (CPython 3.11 counts C
  frames against the limit). The profile's transforms now replace the
  previous ones, as _apply_discovery_mode already did; a test switches
  the profile 600 times and then calls a tool. The local suite runs in
  half the time it took with the stack growing.
- 21 fake-ActiveX tests build a real pywin32 VARIANT; they now skip
  without pywin32, like the suite's other VARIANT-dependent COM tests,
  and the Windows lane keeps running them.
- A test spelled a path through a directory it never created, which only
  Windows normalises away; it creates the directory.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

tests/test_refs_contract.py

@@ -22,6 +22,11 @@ from backends.contracts.refs import (
 )
 from backends.ezdxf_backend import EzdxfBackend
 
+#: A path that marshals a point or an object array builds a real pywin32 VARIANT,
+#: and pywin32 exists only on Windows. The Windows lane runs these; elsewhere
+#: they skip, like the suite's other VARIANT-dependent COM tests.
+needs_pywin32 = pytest.mark.skipif(find_spec("win32com") is None, reason="pywin32 not installed")
+
 TRACK_G_KEYS = ("dwg_write", "xref_live", "xlsx_write")
 
 
@@ -385,6 +390,7 @@ class _ComDoc:
 
 
 @pytest.mark.asyncio
+@needs_pywin32
 async def test_com_attach_calls_the_measured_member_with_radians(monkeypatch, external):
     import math
 
@@ -478,6 +484,7 @@ async def test_com_attach_refuses_a_plain_block_of_the_same_name_case_insensitiv
 
 
 @pytest.mark.asyncio
+@needs_pywin32
 async def test_com_attach_still_works_when_no_block_of_that_name_exists(monkeypatch, external):
     import backends.com_backend as cb
 
@@ -489,6 +496,7 @@ async def test_com_attach_still_works_when_no_block_of_that_name_exists(monkeypa
 
 
 @pytest.mark.asyncio
+@needs_pywin32
 async def test_com_raster_calls_addraster_with_radians(monkeypatch, tmp_path):
     import math