fix: resolve bwrap from trusted PATH entry (#15791)

## Summary
- resolve system bwrap from PATH instead of hardcoding /usr/bin/bwrap
- skip PATH entries that resolve inside the current workspace before
launching the sandbox helper
- keep the vendored bubblewrap fallback when no trusted system bwrap is
found

## Validation
- cargo test -p codex-core bwrap --lib
- cargo test -p codex-linux-sandbox
- just fix -p codex-core
- just fix -p codex-linux-sandbox
- just fmt
- just argument-comment-lint
- cargo clean

codex-rs/linux-sandbox/src/launcher.rs

@@ -10,8 +10,6 @@ use std::sync::OnceLock;
 use crate::vendored_bwrap::exec_vendored_bwrap;
 use codex_utils_absolute_path::AbsolutePathBuf;
 
-const SYSTEM_BWRAP_PATH: &str = "/usr/bin/bwrap";
-
 #[derive(Debug, Clone, PartialEq, Eq)]
 enum BubblewrapLauncher {
     System(SystemBwrapLauncher),
@@ -36,7 +34,10 @@ pub(crate) fn exec_bwrap(argv: Vec<String>, preserved_files: Vec<File>) -> ! {
 fn preferred_bwrap_launcher() -> BubblewrapLauncher {
     static LAUNCHER: OnceLock<BubblewrapLauncher> = OnceLock::new();
     LAUNCHER
-        .get_or_init(|| preferred_bwrap_launcher_for_path(Path::new(SYSTEM_BWRAP_PATH)))
+        .get_or_init(|| match codex_core::config::find_system_bwrap_in_path() {
+            Some(path) => preferred_bwrap_launcher_for_path(&path),
+            None => BubblewrapLauncher::Vendored,
+        })
         .clone()
 }