dotfiles: put .local\bin on the user PATH, and skip VirtualBox in a VM

A new LocalBinPath step puts %USERPROFILE%\.local\bin - where Claude
Code's native installer puts claude.exe - on the user PATH, creating it
if need be. The installer itself only prints a reminder.

VirtualBox is now -NotInVM: when this Windows is itself a guest, the
plan marks it [-] and names the hypervisor, read from the firmware's
SMBIOS manufacturer/model rather than HypervisorPresent, which is also
true on physical hosts running Hyper-V, WSL2 or VBS.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>