Describe the bug
Coverage 7.13.3 raises PermissionError when the project workspace is nested under a directory the user doesn't have read access to. The new virtualenv detection code in _analyze_directory() walks up parent directories and fails when it encounters a restricted directory.

This is a regression introduced by the fix for #2082.

To Reproduce

1. What version of Python are you using?
   Python 3.10
2. What version of coverage.py shows the problem?
   7.13.3 (released 2026-02-03). Version 7.13.2 works fine.
3. What versions of what packages do you have installed?
   • coverage==7.13.3
   • pytest==7.4.4
   • pytest-cov==6.2.1
4. What code shows the problem?
   Any project will reproduce this. The issue is the directory structure, not the code.
5. What commands should we run to reproduce the problem?

   docker run -it --rm python:3.10 bash -c '
   mkdir -p /home/restricted.domain/user/workspace
   useradd -m testuser
   chown -R testuser:testuser /home/restricted.domain/user
   chown root:root /home/restricted.domain
   chmod 711 /home/restricted.domain
   su testuser -c "
   cd /home/restricted.domain/user/workspace
   python -m venv .venv
   . .venv/bin/activate
   pip install -q pytest pytest-cov coverage==7.13.3
   mkdir src tests
   touch src/__init__.py
   echo \"def hello(): return 'world'\" > src/app.py
   echo \"from src.app import hello
   def test_hello(): assert hello() == 'world'\" > tests/test_app.py
   pytest --cov=src tests/
   "
   '

Expected behavior
Coverage should handle inaccessible parent directories gracefully, either by catching PermissionError or stopping the upward traversal when access is denied.

Additional context
This affects CI environments where the build user's home directory is under a domain-based path (e.g., /home/domain.com/builduser/...) where the intermediate directory (/home/domain.com) exists but isn't readable.

The error occurs in inorout.py at line 182 in _analyze_directory(), called from set_matchers_depending_on_syspath().

Workaround: Pin to coverage==7.13.2
Add any other context about the problem here.