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/01-the-copy-paste-problem/README.md

@@ -137,6 +137,12 @@ purpose** so you recognize it later.
 - Python 3.10 or newer (`python --version` or `python3 --version` to check).
 - Your usual AI chat assistant, open in a browser tab.
 
+> **One command name, the whole course through:** whichever of `python` / `python3` just printed a
+> 3.10+ version is the command to use in *every* lab from here on. The labs are written with
+> `python`; if that's "command not found" on your machine — common on current macOS and default
+> Debian/Ubuntu, where Python is installed only as `python3` — read it as `python3` (and `pip3`
+> wherever a lab uses `pip`). This note holds course-wide; we won't repeat it.
+
 ### Get the course materials
 
 Everything you'll run in this course lives in one repo. Grab it once, up front — no tools required
@@ -170,6 +176,10 @@ You now have every module's files locally, including this one's under
 
    (Copy them however you like — drag-and-drop in your editor's file explorer is fine.)
 
+   > **On Windows:** these labs' shell snippets are written for bash — run them from **Git Bash** or
+   > **WSL** and they work as-is. In native PowerShell a few POSIX-only commands differ; here, `mkdir
+   > -p` becomes `New-Item -ItemType Directory -Force`.
+
 2. Open the folder in your editor (`code .` if you're using VS Code, or File → Open Folder).
 
 3. Run it in your terminal to confirm it works: