## Summary
This PR adds two read-only path helpers to `js_repl`:
- `codex.cwd`
- `codex.homeDir`
They are exposed alongside the existing `codex.tmpDir` helper so the
REPL can reference basic host path context without reopening direct
`process` access.
## Implementation
- expose `codex.cwd` and `codex.homeDir` from the js_repl kernel
- make `codex.homeDir` come from the kernel process environment
- pass session dependency env through js_repl kernel startup so
`codex.homeDir` matches the env a shell-launched process would see
- keep existing shell `HOME` population behavior unchanged
- update js_repl prompt/docs and add runtime/integration coverage for
the new helpers
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