[codex] sanitize codex child process env

[seungpyoson]

Summary

• add a shared sanitizeChildEnv helper in plugins/codex/scripts/lib/process.mjs
• route plugin child-process launches through that sanitizer in the direct app-server, broker, detached task worker, and stop-review gate paths
• add regression coverage for the routing-env contract and align the deterministic command-doc test with the current quoted "$ARGUMENTS" command form

Why

This was surfaced by seungpyoson/claude-config#525.

The Codex marketplace plugin was forwarding ambient Rust verification routing variables across plugin process boundaries. The plugin did not expose a shared sanitizer, and downstream boundary tests were correctly identifying that drift.

Impact

• strips routing-intent and cargo target override env vars from plugin child environments
• makes the process-boundary contract explicit in plugin code and tests
• keeps existing launch behavior unchanged apart from environment scrubbing

Validation

• node --test tests/process.test.mjs
• npm test

[seungpyoson]

Requesting adversarial review.

Focus areas:

• child-process env sanitization boundaries
• whether sanitizeChildEnv is applied at every relevant launch surface
• regressions from scrubbing RUST_VERIFICATION_*, BOLT_RUST_VERIFICATION_ROOT, and CARGO_*TARGET_DIR
• whether the new tests actually prove the contract
• whether aligning tests/commands.test.mjs with the current quoted "$ARGUMENTS" command form is correct and minimal

Validation already run on this branch:

• node --test tests/process.test.mjs
• npm test

PR: #190

[seungpyoson]

Follow-up pushed in response to review:

• harden sanitizeChildEnv(...) to scrub keys case-insensitively so mixed-case Windows env keys cannot bypass the filter
• treat null like inherited env input instead of producing an empty env object
• extend tests to cover:
  • CARGO_TARGET_DIR
  • preserved CARGO_HOME
  • case-insensitive key scrubbing
  • inherited-env sanitization when runCommand(...) is called without an explicit env

Latest validation on branch:

• node --test tests/process.test.mjs
• npm test

Both are passing on the updated branch.