have_npm() / run_npm_install() never find npm on Windows (subprocess cannot resolve npm.cmd) #124

Summary

On Windows, readabilipy.utils.have_npm() always returns False even when Node.js and npm are installed and on PATH, so the Readability.js extraction path is unreachable on Windows and the pure-Python fallback is always used.

Environment

• Windows 11 (build 26300), Python 3.13.14
• readabilipy 0.3.0
• Node.js and npm 11.17.0 installed and on PATH; node.exe, npm.cmd and npm.ps1 all present in the Node.js directory; npm --version works from the same shell that spawned Python

Analysis

readabilipy/utils.py:

def have_npm():
    try:
        cp = subprocess.run(
            ["npm", "version"],
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
            check=True
        )
    except FileNotFoundError:
        return False
    return cp.returncode == 0

On Windows npm ships as npm.cmd / npm.ps1, not npm.exe. subprocess.run(["npm", ...]) does not resolve those shims, so it raises FileNotFoundError, have_npm() returns False, and every extraction prints:

Warning: A working NPM installation was not found. The package will use Python-based article extraction.
Warning: node executable not found, reverting to pure-Python mode. Install Node.js v10 or newer to use Readability.js.

The same resolution problem applies to subprocess.run(["npm", "install"], ...) in run_npm_install().

Suggested fix

Resolve the executable first with shutil.which("npm") - it returns the npm.cmd path on Windows and the plain npm path elsewhere - and invoke the resolved path in both have_npm() and run_npm_install().

Impact

Every Windows user silently gets the pure-Python extractor. In particular, mcp-server-fetch (modelcontextprotocol/servers) documents that installing Node.js makes it "use a different HTML simplifier that is more robust" - on Windows that never actually happens.