Disable auth check for local-only skill flags

Add cmdutil.DisableAuthCheckFlag for --from-local on install so that
installing from a local directory does not require authentication.
This follows the same pattern used by attestation verify for its
--bundle flag.

The --dry-run flag on publish is intentionally left with auth enabled
because dry-run validation includes remote repository checks (security
settings, tag protection, topics).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

pkg/cmd/skills/install/install.go

@@ -199,6 +199,7 @@ func NewCmdInstall(f *cmdutil.Factory, runF func(*InstallOptions) error) *cobra.
 	cmd.Flags().StringVar(&opts.Dir, "dir", "", "Install to a custom directory (overrides --agent and --scope)")
 	cmd.Flags().BoolVarP(&opts.Force, "force", "f", false, "Overwrite existing skills without prompting")
 	cmd.Flags().BoolVar(&opts.FromLocal, "from-local", false, "Treat the argument as a local directory path instead of a repository")
+	cmdutil.DisableAuthCheckFlag(cmd.Flags().Lookup("from-local"))
 
 	return cmd
 }