internal/pkg: pass context to file cure

This removes the left over embedded contexts.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg_test.go

@@ -109,7 +109,7 @@ type stubFile struct {
 	stubArtifact
 }
 
-func (a stubFile) Cure() ([]byte, error) { return a.data, a.err }
+func (a stubFile) Cure(context.Context) ([]byte, error) { return a.data, a.err }
 
 // newStubFile returns an implementation of [pkg.File] with hardcoded behaviour.
 func newStubFile(