Document python vs python3 on Windows

[dchaudhari7177]

Closes #4. Documentation only — one note in README.md, placed directly under the requirements table and next to the existing "Works on macOS, Linux and Windows" claim, since that sentence is what makes the mismatch surprising.

What actually happens

I checked this on Windows 11 rather than describing it from memory, and the real failure is worse than the "command not found" the issue anticipates:

$ where python3
C:\Users\...\AppData\Local\Microsoft\WindowsApps\python3.exe

$ where python
C:\Users\...\AppData\Local\Programs\Python\Python312\python.exe

python3 does resolve — to the Microsoft Store app-execution alias stub. Running it prints:

Python was not found; run without arguments to install from the Microsoft Store,
or disable this shortcut from Settings > Apps > Advanced app settings > App execution aliases.

and exits. So a reader with a perfectly good Python 3.12 on PATH is told Python was not found, and sent off to reinstall Python — which will not help, because the problem is the command name, not the interpreter. That is a worse trap than a bare "not found", so the note names the message explicitly to make it recognisable.

py is also present (C:\Windows\py.exe), so the note offers both.

I confirmed the scripts themselves are fine under the right name — python scripts/build_graph.py examples/sample-vault --out ... runs clean on Windows:

wikilink edges resolved: 15
awaiting model extraction: 6
written: ...

So this really is only a naming issue, and a one-line docs fix is the whole of it.

What I did not do

I left the ~9 python3 occurrences in the code blocks alone. Rewriting them to python would break macOS and Linux readers, where python may be absent or Python 2, and adding a second Windows variant to every block would triple the command list to say one thing. One substitution rule stated once seemed the better trade — happy to do it differently if you prefer.

[jessicahiggs]

Merged — thank you.

Testing this on an actual Windows machine rather than describing it from the issue was the right call, and it turned up something the issue got wrong: I assumed a clean command not found, and the real behaviour is worse. python3 resolving to a Store stub that says "Python was not found" would send someone off reinstalling a Python they already have.

Naming that exact message is what makes the note findable by someone already staring at it. Good judgement on leaving the ~9 python3 occurrences alone too — one substitution rule stated once is the right trade.