* fix(generation): refuse supplied media fields a provider cannot carry
* fix(media): probe selected tools in their execution environment
* fix(credentials): use native file replacement across processes
* fix(runtime): distinguish tool preparation from process startup
* fix(cli): bootstrap from the physical distribution directory
`sh -c` cost these fixtures a shell twice over. It is not on a Windows machine
by default, and where Git for Windows puts it on PATH the file half-works, which
is worse than failing: a temporary path interpolated into the command string
arrives with its backslashes eaten, so the marker was written somewhere nobody
looked and `up` waited its full twenty seconds before reporting the program
unchanged.
Node is here by definition and takes its arguments as arguments rather than as
text to be parsed a second time, so the marker path is passed rather than
spelled. The command-name assertion now checks both halves of what it is named
for — that the detail says which command failed, and that it says why — instead
of a spelling of the interpreter that only holds on one platform.
kashorin