fix(ssh-key): title keys by their comment and recognize private keys

ssh-key create - required --title although the key carries a comment,
and a private key failed with "supply exactly one valid SSH public key".
The title now defaults to the key comment, then the computer's name, the
file argument is optional (stdin when piped), and a private key points to
its .pub file. Adding a registered key names the key it duplicates.

ssh-key list shows ID, TITLE, FINGERPRINT and ADDED with a header, view
shows the key instead of its list row, delete asks with the key's title
and fingerprint, and mutations print ✓ lines. create gains the gh alias
add and -t for --title, key IDs complete, and every command has examples.

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

internal/app/app_test.go

@@ -557,10 +557,6 @@ const (
 	secret delete
 	secret list
 	secret set
-	ssh-key create
-	ssh-key delete
-	ssh-key list
-	ssh-key view
 	status
 	time create
 	time delete
@@ -603,7 +599,6 @@ const (
 	run artifact
 	search
 	secret
-	ssh-key
 	time
 	variable
 	wiki