fix file names for claude commands

[svenwltr]

Go does not like those file names.

❯ go get github.com/rebuy-de/rebuy-go-sdk/v9@optional-assets
go: downloading github.com/rebuy-de/rebuy-go-sdk/v9 v9.0.1-0.20250708095442-9624a66fb28f
go: github.com/rebuy-de/rebuy-go-sdk/v9@optional-assets: create zip: .claude-commands/rebuy-go-sdk:docs.md: malformed file path ".claude-commands/rebuy-go-sdk:docs.md": invalid char ':'
.claude-commands/rebuy-go-sdk:verify-server.md: malformed file path ".claude-commands/rebuy-go-sdk:verify-server.md": invalid char ':'