Policy bypass: shell-wrapper flags skip inner command re-check

## Summary

`stripShellWrapper` only recognizes bare `bash -c` / `powershell [-NoProfile] -Command`. With any extra wrapper flag (`bash -x -c`, `bash --noprofile -c`, `powershell -NoProfile -ExecutionPolicy Bypass -Command`, combined `-xc`), the input comes back unchanged — and the policy engine only re-checks the inner command when stripping changed something. So the inner command escapes all policy scrutiny while the gate sees just `bash` / `powershell`.

Real runs:

- `stripShellWrapper('bash -c "rm -rf /"')` → `'rm -rf /'` (re-checked)
- `stripShellWrapper('bash -x -c "rm -rf /"')` → unchanged (never re-checked)
- `stripShellWrapper('powershell -NoProfile -ExecutionPolicy Bypass -Command "..."')` → unchanged

## Root cause

The wrapper regex enumerates exact flag sequences instead of tolerating the flags each shell accepts before `-c` / `-Command`.

## Expected

Wrapper flags (short clusters incl. combined `-xc`, long options, `-Name value` pairs) are tolerated so the inner command is always what the policy sees. Known residual: `-X value` pairs with a space-separated value on POSIX (`bash -o pipefail -c`) still don't strip.

Start by locating stripShellWrapper and the policy-engine call site that conditionally re-checks the inner command. Read the existing wrapper regex and its tests, then cover extra shell flags, combined short flags, and PowerShell option pairs; done means these forms expose the inner command for policy checks while the stated POSIX -X value case remains a known residual.

Written by the indexing model from the issue text.