fix(org): check membership before member changes and polish org output

org member remove and public/private exited 0 without a word for users
who are not members, and member list --public showed concealed members,
because Gitea lists them as public to administrators. Membership changes
now check the membership first: removing a non-member warns, publicizing
one fails, and a change to the current visibility warns. Member list
checks each membership and gains a VISIBILITY column.

org list and member list get a header and context line through
writeTable, org view shows the description, website, location and member,
team and repository counts, mutations print ✓ lines, and org delete asks
to type the organization's name after refusing organizations that still
own repositories. public and private become publicize and conceal, the
old names stay as aliases, and org edit --visibility no longer shows the
create default. Every command has examples, and organizations and members
complete.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/completion.go

@@ -445,8 +445,8 @@ func (a *application) completeReleases() cobra.CompletionFunc {
 // completeOrgs completes the organizations of the account.
 func (a *application) completeOrgs() cobra.CompletionFunc {
 	return a.apiCompletion(false, func(ctx context.Context, t target, _ string) ([]cobra.Completion, error) {
-		items, _, err := services.Organizations{Client: t.client}.List(ctx, true, "", completionLimit, 1)
-		return describe(items, func(item services.Organization) (string, string) { return item.Name, item.FullName }), err
+		items, err := services.Organizations{Client: t.client}.List(ctx, true, "", completionLimit, 1)
+		return describe(items.Items, func(item services.Organization) (string, string) { return item.Name, item.FullName }), err
 	})
 }