Add telemetry for the Windows system config namespace (#44284)

## What changed

Probe the default Windows system config namespace at session start and record `codex.windows_system_config.namespace_squatting_probe` once per process when metrics are available.

When `config.toml` or `requirements.toml` exists, check the containing directories for expected ownership and broad standard-user mutation allow ACEs, including permissions inherited by child files. Report coarse results for missing files, expected directories, unexpected types or owners, mutation permissions, and check errors.

The probe is observational: it does not change configuration loading or enforce a trust decision.

GitOrigin-RevId: e1c79dca5548e16e83c7b84b44ab0de4e2643d0d

codex-rs/core/src/session/session.rs

@@ -1143,7 +1143,7 @@ impl Session {
                 model: Some(session_model.clone()),
                 slug: Some(session_model),
             };
-            config.features.emit_metrics(&session_telemetry);
+            crate::config::emit_session_start_metrics(config.as_ref(), &session_telemetry);
             let is_worktree = session_configuration.cwd().canonicalize().ok().and_then(|cwd| {
                 codex_git_utils::repository_identity(&cwd).and_then(|_| {
                     get_git_repo_root(&cwd).map(|root| root.join(".git").is_file())