Support Unix socket allowlists in macOS sandbox (#17654)

## Changes

Allows sandboxes to restrict overall network access while granting
access to specific unix sockets on mac.

## Details

- `codex sandbox macos`: adds a repeatable `--allow-unix-socket` option.
- `codex-sandboxing`: threads explicit Unix socket roots into the macOS
Seatbelt profile generation.
- Preserves restricted network behavior when only Unix socket IPC is
requested, and preserves full network behavior when full network is
already enabled.

## Verification

- `cargo test -p codex-cli -p codex-sandboxing`
- `cargo build -p codex-cli --bin codex`
- verified that `codex sandbox macos --allow-unix-socket /tmp/test.sock
-- test-client` grants access as expected

codex-rs/Cargo.lock

@@ -1694,6 +1694,7 @@ dependencies = [
  "codex-stdio-to-uds",
  "codex-terminal-detection",
  "codex-tui",
+ "codex-utils-absolute-path",
  "codex-utils-cargo-bin",
  "codex-utils-cli",
  "codex-utils-path",
@@ -2694,6 +2695,8 @@ dependencies = [
 name = "codex-sandboxing"
 version = "0.0.0"
 dependencies = [
+ "anyhow",
+ "async-trait",
  "codex-network-proxy",
  "codex-protocol",
  "codex-utils-absolute-path",
@@ -2702,6 +2705,7 @@ dependencies = [
  "pretty_assertions",
  "serde_json",
  "tempfile",
+ "tokio",
  "tracing",
  "url",
  "which 8.0.0",