## Why
`CODEX_EXEC_SERVER_NOISE_AUTH_TOKEN` is an execution-server credential and
must not be exposed to model-reachable commands or command hooks, including
when shell environment policy explicitly sets a case variant of the name.
## What changed
- Add `CODEX_EXEC_SERVER_NOISE_AUTH_TOKEN` to the shared list of
non-inheritable environment variables.
- Keep the environment variable constant in `codex-protocol` so the exec
server and environment scrubber use the same definition.
- Verify case-insensitive removal after policy overrides for shell commands
and command hooks.
GitOrigin-RevId: 759b224b6a7fb4f56f7b1a6d94ffbb0b188c658f