* fix(commit-message): keep Windows paths intact in agent command overrides
`tokenizeCustomCommandTemplate` applies POSIX backslash-escape rules on every
platform. On Windows `\` is the path separator, so a native absolute path in an
agent command override is silently destroyed:
C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
-> C:WindowsSystem32WindowsPowerShellv1.0powershell.exe
which is then reported as not found on PATH. The agent *startup* path already
routes Windows shells to the Windows tokenizer, but the commit-message AI path
still calls the generic tokenizer directly, so overrides, extra CLI args and
custom commands there are all affected.
The tokenizer gains an explicit `'escape' | 'literal'` mode rather than reading
`process.platform`, because the same template can be parsed on one host and
executed on another. `'escape'` stays the default, so POSIX behaviour — where
`foo\ bar` is deliberately one token — is unchanged.
`'literal'` is selected only where the command provably runs on native Windows:
a LOCAL target, on win32, with no WSL distro. A WSL target runs a Linux binary
inside the distro, and a remote target runs on a host whose platform this
process cannot see; both keep POSIX escaping.
Fixes#11375
* test: pin the platform decision for literal-backslash parsing
commandBackslashMode is the only place that reads the platform, so it is where
this can be wrong in the direction that matters — applying Windows rules to a
command that will actually run under a POSIX shell. WSL and remote targets are
pinned explicitly; both were previously untested.
