feat(plugin): proxy Composer\Util\Filesystem into the plugin worker

The class was shadowed by a guard, so a plugin doing `new Filesystem()`
got an explicit error. It is classified rust-proxy and plugin-constructible
and the Rust port is complete, so listing it as a stub target and answering
its public surface from the entity is all it takes.

The constructor rejects a caller-supplied ProcessExecutor: that class has no
proxy stub, so the argument could only be a second instance the Rust side
never sees. findShortestPath re-checks its arguments at the boundary because
the port panics where PHP throws, and a panic would take the process down
instead of reaching the plugin's catch block.

phpstan/extension-installer matches upstream Composer byte for byte again.

0 files changed, 0 insertions, 0 deletions