Keep Unix-only stdlib out of CLI and pytest import paths

[brainRottedCoder]

Summary

• Stop importing fcntl / pty / termios / tty at module scope so pytest can collect on Windows and import wmo.cli.app works.
• Keep PTY child runners and Darwin FD probes POSIX-only via skip/local import.
• Add an AST and subprocess import gate so the boundary cannot regress.
  Fixes pytest cannot collect on Windows: wmo/conftest.py imports Unix-only fcntl #532

Test plan

• uv run ruff check .
• uv run ruff format --check .
• uv run ty check (Ubuntu CI; Windows ty still fails on POSIX stubs)
• uv run pytest -q wmo/tests/posix_stdlib_import_test.py wmo/cli/shared/picker_test.py wmo/cli/judge/trace_viewer_test.py
• uv run python -c "import wmo.cli.app; import wmo.conftest"
• uv run pytest --collect-only -q wmo

[greptile-apps]

Greptile Summary

The PR defers Unix-only standard-library imports to POSIX helpers, adds non-POSIX skips, and introduces package-wide import regression checks. The installed-release evidence path remains capable of invoking the PTY helper on Windows.

• Moves terminal-specific imports out of CLI and pytest module scope.
• Adds POSIX gating for keyboard and pseudo-terminal tests.
• Adds AST scanning and subprocess smoke coverage for import safety.

Confidence Score: 4/5

The PR is not yet safe to merge because the installed-release evidence test still reaches Unix-only PTY imports during a Windows pytest run.

The direct terminal-close-race test now skips correctly, but the undecorated installed-wheel evidence test executes a copied driver whose interactive flow calls _run_tty_child and imports unavailable POSIX modules.

Files Needing Attention: exp/tests/release_test.py

Important Files Changed

Filename	Overview
exp/tests/release_test.py	Defers PTY imports and guards the race test, but the installed-wheel evidence test still reaches the POSIX-only helper on Windows.
exp/tests/posix_stdlib_import_test.py	Adds package-wide module-scope import enforcement, with a non-blocking gap for except* statement bodies.
exp/conftest.py	Defers POSIX imports and skips the terminal-child fixture on non-POSIX hosts.
exp/cli/shared/picker.py	Defers terminal imports and routes Windows consoles through the line-based picker.
exp/cli/judge/trace_viewer.py	Moves terminal-only imports into the raw-key helper.

_{Reviews (3): Last reviewed commit: "Keep Unix-only stdlib out of CLI and pyt..." | Re-trigger Greptile}