Prevent launch context from reaching child processes (#37607)

## Why

Model-reachable child processes should not inherit Codex launch context.

## What changed

- Treat `OPENAI_FEDERATION_RULE_ID` and `OPENAI_IDENTITY_TOKEN_FILE` as non-inheritable environment variables, with case-insensitive matching.
- Remove them after shell environment policy overrides and before spawning commands across execution, MCP, hooks, Git helpers, and remote helper processes.

## Testing

- Cover inherited and explicitly configured variants, including mixed-case names.
- Verify the variables are absent from real child environments and app-server command and process execution.

GitOrigin-RevId: 2535527893985fef0995617f4c5b2462bea7c136

codex-rs/git-utils/src/operations.rs

@@ -120,6 +120,7 @@ where
         }
     }
     command.args(&args_vec);
+    crate::scrub_non_inheritable_environment(&mut command);
     let output = command.output()?;
     if !output.status.success() {
         let stderr = String::from_utf8_lossy(&output.stderr).trim().to_string();