feat: exec policy integration in shell mcp (#7609)

adding execpolicy support into the `posix` mcp

Co-authored-by: Michael Bolin <mbolin@openai.com>

codex-rs/Cargo.lock

@@ -1256,6 +1256,7 @@ dependencies = [
  "async-trait",
  "clap",
  "codex-core",
+ "codex-execpolicy",
  "libc",
  "path-absolutize",
  "pretty_assertions",