## Why
Memory read telemetry currently reconstructs the executable shell
command after a tool call finishes. That duplicates shell, login-policy,
and cwd resolution owned by the tool handlers, and can diverge from the
environment-specific command that unified exec actually ran.
## What changed
- Expose the existing restricted shell-script parser directly for raw
script text.
- Parse `shell_command` and `exec_command` input into plain command argv
before classifying memory reads.
- Preserve all-or-nothing safe-command validation for multi-command
scripts.
- Remove cwd resolution, shell selection, and the unnecessary async
boundary from memory read metric emission.
## Testing
- `just test -p codex-shell-command`
- `cargo check -p codex-core`
## Summary
- collapse parsed command output to a single `Unknown` whenever the
normal parse includes any unknown entry
- preserve the existing parsing flow and existing `cd` handling,
including the current `cd && ...` collapse behavior
- trim redundant tests and add focused coverage for collapse-on-unknown
cases
## Testing
- `cargo test -p codex-shell-command`
