chore: fix dead_code in pet-winpython on non-Windows and lint all OSes

discover_environments_in and collect_install were gated
cfg(any(windows, test)), but every caller (production and tests) is
cfg(windows), so non-Windows test builds saw them as dead code. Gate
them as cfg(windows) to match their callers.

Verified clean via cross-target clippy for linux-gnu, apple-darwin and
the host (windows). Add macOS to the lint matrix now that it is clean.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: karthiknadig

.github/workflows/lint.yml

@@ -36,6 +36,7 @@ jobs:
         os:
           - ubuntu-latest
           - windows-latest
+          - macos-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v4

crates/pet-winpython/src/lib.rs

@@ -382,7 +382,7 @@ fn discover_environments(locator: &WinPython) -> Vec<PythonEnvironment> {
 
 /// Testable variant of [`discover_environments`] that takes the list of
 /// search paths as input rather than reading environment variables.
-#[cfg(any(windows, test))]
+#[cfg(windows)]
 fn discover_environments_in(
     locator: &WinPython,
     search_paths: Vec<PathBuf>,
@@ -430,7 +430,7 @@ fn discover_environments_in(
     found
 }
 
-#[cfg(any(windows, test))]
+#[cfg(windows)]
 fn collect_install(
     winpython_root: &Path,
     locator: &WinPython,