feat: picking the key shares, with no second popup

The picker already shows what's shared. The confirmation stays for a
key from share.key, which wasn't picked. The share format's version
is documented as kept readable.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/ui/app/sharefiles.go

@@ -137,13 +137,13 @@ func (m *Model) confirmShare(s sharing) {
 	})
 }
 
-// pickShareKey asks which secret to encrypt with, in Go to.
+// pickShareKey asks which secret to encrypt with, in Go to, then shares
+// with it.
 func (m *Model) pickShareKey(s sharing) tea.Cmd {
 	cmd := m.openGoTo(tabSearch, true)
 	m.search.pick = func(m *Model, key ref.Ref) tea.Cmd {
 		s.key = key
-		m.confirmShare(s)
-		return nil
+		return m.seal(s) // the picker showed what's shared
 	}
 	m.search.pickTitle = shareTitle(s)
 	m.search.pickLines = append(m.sharedFiles(s), "",