[codex] honor sync child_process numeric stdio fds

[andrewtdiz]

Refs #2555.

Summary

• Parse sync options.stdio string/array forms for spawnSync(), execFileSync(), and execSync(), including numeric fd entries.
• Route numeric stdio fds through Perry's registered fs.openSync() file table, with a Unix raw-fd fallback for externally supplied descriptors.
• Return Node-shaped null stdout/stderr slots when sync stdout/stderr are not piped.
• Add a Node-suite parity fixture for sync stdout/stderr fd routing, thrown execFileSync() errors, and stdin fd input.

Scope

This is a narrow sync-only slice of #2555. It intentionally leaves live spawn() / fork() numeric fds to #4284 and keeps custom stream handles, invalid-fd validation, AbortSignal/killSignal, uid/gid, detached/platform flags, and broad option validation out of this cut.

Validation

• PASS: PATH="/root/.npm/_npx/bac97da9607b7ef2/node_modules/node/bin:$PATH" node --experimental-strip-types test-parity/node-suite/child_process/sync/sync-stdio-fd.ts
• PASS: PERRY_ALLOW_UNIMPLEMENTED=1 PERRY_NO_AUTO_OPTIMIZE=1 PERRY_RUNTIME_DIR=/root/perry-worktrees/perry-node-child-process-stdio-fd-tail/target/debug target/debug/perry compile --no-cache test-parity/node-suite/child_process/sync/sync-stdio-fd.ts -o /tmp/perry_sync_stdio_fd_debugrt
• PASS: /tmp/perry_sync_stdio_fd_debugrt
• PASS: CARGO_TARGET_DIR=/root/perry-worktrees/.build-targets/perry-child-stdio-fd-check cargo check -p perry-runtime (existing warnings)
• PASS: cargo build -p perry-runtime (existing warnings)
• PASS: cargo fmt --all -- --check
• PASS: git diff --check
• PASS: ./scripts/check_file_size.sh

The full focused run_parity_tests.sh --suite node-suite --module child_process --filter sync-stdio-fd path could not complete in this environment because the required release compiler/runtime build terminated before producing a binary/report and emitted no Rust diagnostic. The fixture was therefore verified through a direct no-cache Perry compile/run linked against the freshly built debug runtime archive.

[proggeramlug]

Superseded by the merged combination of #4284 (CpStdio::Fd + cp_stdio_from_fd + fs::try_clone_registered_fd), #4301 (cp_read_spawn_sync_run_options), and #4304 (cp_read_sync_stdio_run_options). On current main all three sync entry points already read fd-aware stdio — js_child_process_exec_sync and js_child_process_exec_file_sync call cp_read_sync_stdio_run_options, js_child_process_spawn_sync calls cp_read_spawn_sync_run_options, and cp_run_to_completion maps CpStdio::Fd → cp_stdio_from_fd. So numeric stdio fds work end-to-end in the sync APIs without this PR's competing cp_stdio_from_kind refactor. Closing as duplicate.