fix(portability): one python/python3 note + cross-shell guidance for bash-only labs

- M1: single prominent note that the command may be python3/pip3 (modern macOS,
  default Debian/Ubuntu); referenced rather than repeated.
- Cross-shell notes where bash-only commands appear: M1 mkdir -p, M12 rm -f,
  M16 bind-mount (braced ${PWD} + PowerShell note), M19 inspect-runner.sh gains a
  timeout/gtimeout/bash-native fallback so it doesn't hang on stock macOS.

Closes #31
Closes #32

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

modules/12-revert-reset-and-recovery/README.md

@@ -305,6 +305,10 @@ do them once on purpose now.
    git log --oneline                             # the bad merge is STILL there, with a revert after it
    ```
 
+   > **On Windows:** `rm -f` is bash. Run this lab from Git Bash or WSL (it works as-is), or use
+   > PowerShell's `Remove-Item -Force tasks.json`. Every other command here is Git, identical across
+   > shells.
+
    That last point is the whole lesson: you undid the effect **without rewriting history**. Anyone who
    pulled the bad merge just pulls your revert on top and they're fine.