fix: generate suggestions for invalid arg instead of args[0] in OnlyValidArgs

[aoright]

Problem

In OnlyValidArgs, when validating positional arguments in the loop for _, v := range args, if an argument v is invalid, the error message generated suggestions via cmd.findSuggestions(args[0]) instead of cmd.findSuggestions(v). In multi-arg invocations where the first argument was valid and subsequent arguments were invalid, suggestions were computed against args[0] rather than the invalid argument v.

Solution

• Pass v to cmd.findSuggestions(v) in OnlyValidArgs.
• Add TestOnlyValidArgs_WithValidAndInvalidArgs test case in args_test.go.

[CLAassistant]

All committers have signed the CLA.