Fix test collection and execution errors on Windows (geteuid, FileStore skip, bedrock tempfile lock) #2027

Summary

Running the test suite on Windows (or collecting tests with pytest) encounters multiple crashes and collection failures due to POSIX assumptions in tests:

1. AttributeError: module 'os' has no attribute 'geteuid' during test collection:
   In tests/lib/tools/test_file_store.py:207, 317 and tests/lib/tools/memory_sync/test_delete_discipline.py:168:

   @pytest.mark.skipif(os.geteuid() == 0, reason="permission checks do not bind root")

   Because os.geteuid does not exist on Windows, evaluating it in the decorator during pytest module import crashes collection immediately:

   AttributeError: module 'os' has no attribute 'geteuid'
   

   This prevents pytest from discovering or running any subsequent tests.

2. Unskipped POSIX-only FileStore suites:
   FileStore explicitly requires _O_NOFOLLOW != 0 (_platform_supported()) and raises RuntimeError("FileStore requires O_NOFOLLOW support on this platform") on non-POSIX platforms. test_file_store.py carries:

   pytestmark = pytest.mark.skipif(os.name != "posix", reason="FileStore refuses non-POSIX platforms")

   However, tests/lib/tools/memory_sync/test_memory_sync.py and tests/lib/tools/memory_sync/test_delete_discipline.py were missing this file-level marker, causing 38 test failures on Windows.

3. tempfile.NamedTemporaryFile file-locking contention in mock_aws_config:
   In tests/lib/test_bedrock.py:65:

   with tempfile.NamedTemporaryFile(mode="w+", delete=True) as temp_file:
       ...
       monkeypatch.setenv("AWS_CONFIG_FILE", str(temp_file.name))
       yield

   On Windows, an open NamedTemporaryFile(delete=True) cannot be opened by a second handle (boto3.Session). boto3 encounters a PermissionError [Errno 13], which botocore catches and translates to botocore.exceptions.ProfileNotFound, causing 4 test failures:

   • test_region_infer_from_profile
   • test_region_infer_from_specified_profile[default profile]
   • test_region_infer_from_specified_profile[custom profile]
   • test_region_infer_from_aws_profile_argument[profiles0]

4. Missing @needs_symlinks marker on symlink tests:
   In tests/lib/tools/test_agent_toolset.py, three tests (test_read_through_symlink_escape_is_rejected, test_glob_post_filters_symlink_escape, and test_grep_skips_symlinked_files) create symlinks without carrying the @needs_symlinks marker, failing on Windows machines where symlink privileges are restricted (OSError: [WinError 1314]).

Expected Behavior

• Guard os.geteuid() with os.name != "posix" so non-POSIX platforms skip cleanly without collection crashes.
• Mark memory sync suites to skip on non-POSIX platforms matching test_file_store.py.
• Use pytest's tmp_path fixture for mock_aws_config in test_bedrock.py to avoid Windows file-locking contention.
• Apply @needs_symlinks to the remaining symlink tests in test_agent_toolset.py.