refactor: use hypeman-go SDK for cp operations

Refactor cp command to use the SDK's lib.CpToInstance and lib.CpFromInstance
instead of duplicating WebSocket handling logic.

Changes:
- Replace copyFileToInstance with SDK call
- Replace copyDirToInstance with SDK call
- Replace copyFromInstance with SDK call
- Remove unused createDirOnInstance function
- Remove unused syscall import
- Add replace directive for local hypeman-go (for development)

This reduces code duplication and ensures bug fixes and features
in the SDK are automatically available in the CLI.

Author: rgarcia

go.mod

@@ -74,3 +74,5 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20250825161204-c5933d9347a5 // indirect
 	google.golang.org/grpc v1.75.1 // indirect
 )
+
+replace github.com/onkernel/hypeman-go => /home/raf/code/hypeman-go

go.sum

@@ -105,8 +105,6 @@ github.com/muesli/reflow v0.3.0 h1:IFsN6K9NfGtjeggFP+68I4chLZV2yIKsXJFNZ+eWh6s=
 github.com/muesli/reflow v0.3.0/go.mod h1:pbwTDkVPibjO2kyvBQRBxTWEEGDGq0FlB1BIKtnHY/8=
 github.com/muesli/termenv v0.16.0 h1:S5AlUN9dENB57rsbnkPyfdGuWIlkmzJjbFf0Tf5FWUc=
 github.com/muesli/termenv v0.16.0/go.mod h1:ZRfOIKPFDYQoDFF4Olj7/QJbW60Ol/kL1pU3VfY/Cnk=
-github.com/onkernel/hypeman-go v0.7.0 h1:KUeY4VGJtStA4+zkPtx7eDCO3rSznbIVoj4U6l+g50Q=
-github.com/onkernel/hypeman-go v0.7.0/go.mod h1:BPT1yh0gbby1E+As/xLM3GVjw7752+2C5SaEiJV9rRc=
 github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
 github.com/opencontainers/image-spec v1.1.1 h1:y0fUlFfIZhPF1W537XOLg0/fcx6zcHCJwooC2xJA040=