feat: put ncp on PATH on both platforms; rename WSL reqs to Windows

Ports the ncp PATH work from upstream. Registering ncp as a shell-profile
function failed three ways on Windows: the default Restricted execution policy
blocks the profile itself, profiles don't exist outside PowerShell (cmd, Win+R,
Task Scheduler), and the self-elevating installer writes the admin's profile.

Windows now ships management/ncp.cmd and the installer appends management\ to
the Machine PATH via [Environment]::SetEnvironmentVariable -- never setx, which
truncates PATH at 1024 chars. A .cmd is exempt from the execution policy.

Linux symlinks /usr/local/bin/ncp -> management/nexus-cli.sh, falling back to
the old .bashrc function when sudo is unavailable.

Also renames requirements-wsl.txt to requirements-windows.txt and purges stale
WSL references, including vite.config.js's dev-server comment and
controlpanel.py's "Check WSLg." error string.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bin/panel/install.sh

@@ -41,7 +41,7 @@ cp -f "$NEXUS/management/panel/genmon-16.rc" "$PANEL_CFG/genmon-16.rc"
 # ── Register the genmon applets into the XFCE panel ────────────────────────
 # The network applet's genmon (plugin-13) was added by hand once; the Nexus
 # (15) and Bluetooth (16) applets are wired up programmatically via xfconf so a
-# fresh install picks them up. No-op on machines without XFCE (e.g. the WSL box).
+# fresh install picks them up. No-op on machines without XFCE (e.g. the Windows box).
 # place = before|after — where to insert relative to the network applet (13).
 register_genmon() {
     local id=$1 place=$2 anchor=13 panel=panel-1