test(api,daemon,skills): skipif(win32) for Linux-only tests (green CI Windows)

Once the collection-level blockers were fixed, the Windows runner finally ran the
suite and surfaced 7 pre-existing failures — all tests asserting Linux-only
behavior, while the production code already handles non-Linux gracefully:

- api test_secrets: chmod(0o000) can't make a file unreadable to its owner on
  Windows (the 'unreadable -> None' precondition is unreachable)
- daemon test_scheduler_cron: patches fcntl.flock; fcntl is None on Windows
  (scheduler_cron already skips locking on non-Unix)
- skills test_runner: system_status memory/uptime/processes/summary read Linux
  /proc (skill returns a graceful error on Windows; disk test stays, it's portable)

Guard each with @pytest.mark.skipif(sys.platform == 'win32', reason=...). 68
tests pass on Linux, ruff clean, api+daemon audit 100%.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/aipass/api/tests/test_secrets.py

@@ -33,9 +33,12 @@ Tests — api_key.py (get_secret_cmd):
 from __future__ import annotations
 
 import json
+import sys
 from pathlib import Path
 from unittest.mock import patch, MagicMock
 
+import pytest
+
 from aipass.api.apps.modules.api_key import handle_command as _hc  # noqa: F401 — seedgo test_coverage detection
 from aipass.api.apps.handlers.auth.secrets import (
     get_secret,
@@ -140,6 +143,10 @@ class TestGetSecret:
         assert result is None
         mock_logger.warning.assert_called()
 
+    @pytest.mark.skipif(
+        sys.platform == "win32",
+        reason="chmod(0o000) does not make a file unreadable to its owner on Windows",
+    )
     def test_unreadable_file_returns_none(self, tmp_path: Path) -> None:
         """OSError when reading file returns None."""
         provider_dir = tmp_path / "telegram"