docs: shorten help and migration texts to gh-like brevity

Long texts no longer restate the flag list, the instance selection
of tea help environment, the config keys with descriptions or the
team argument rules shown under ARGUMENTS; webhook events come from
services.WebhookEvents; the migration guide refers to tea help
formatting for the terminal layout.

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

internal/app/notifications.go

@@ -26,11 +26,8 @@ type notificationScope struct {
 }
 
 func (a *application) notificationCommand() *cobra.Command {
-	group := &cobra.Command{Use: "notification", Short: "Read and triage your notifications", Long: `Read and triage the notifications of your account.
-
-Commands act on your whole inbox. -R OWNER/REPO limits them to one repository, and
---this-repo to the repository of the current directory. The IDs that tea notification
-list shows identify notification threads; they are not issue numbers.`}
+	group := &cobra.Command{Use: "notification", Short: "Read and triage your notifications", Long: `Read and triage the notifications of your account, across your whole inbox unless -R or
+--this-repo selects a repository. IDs identify notification threads, not issue numbers.`}
 	var mine, thisRepo bool
 	group.PersistentFlags().BoolVar(&mine, "mine", false, "Read your whole inbox (the default)")
 	_ = group.PersistentFlags().MarkHidden("mine")