* fix(ssh): probe npm via prepended PATH, not colocated with node (#9165)
The remote Node/npm toolchain gate invoked npm by its absolute path
<nodeBinDir>/npm (POSIX) / npm.cmd (Windows, behind a Test-Path
colocation check). But deploy (commandWithNodePath) runs bare `npm`
with nodeBinDir merely prepended to PATH, so npm can resolve from
anywhere on PATH.
A host whose only resolvable node has npm elsewhere on PATH (e.g. node
symlinked into a dir without npm) deployed fine on v1.4.144, but after
upgrade the candidate is rejected with no fallback → SSH/relay
connection fails to establish.
Make the probe resolve npm exactly the way deploy does — bare
`npm --version` under the same prepended PATH — so it still confirms npm
is runnable (the #8450 concern) without requiring colocation. Windows
now prepends the backslash-form dir (matching deploy) so bare-command
PATH lookup resolves reliably.
* test(ssh): cover split Node npm PATH resolution
Brennan Benson
3e276d78ba