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/config.go

@@ -175,28 +175,12 @@ Preferences live in config.yml and instance settings in hosts.yml, in the config
 directory ($TEA_CONFIG_DIR, or tea under the XDG config directory); tea config path prints
 both files. Environment variables that override settings are listed in tea help environment.
 
-Preferences (tea config set <key> <value>):
-  default_host  instance used when no --host, environment variable or repository selects one
-  git_protocol  https or ssh, for clone and checkout remotes
-  editor        command that edits bodies
-  prompt        enabled or disabled
-  pager         command that pages long output
-  browser       command that opens web pages; never disables opening
-  color         auto, always or never
-  hyperlinks    auto, always or never: link the first column of lists to its web page
-  markdown      auto or raw: render markdown bodies on a terminal, or print them as written
-  remote        Git remote that selects the repository
-  aliases       command shortcuts; manage them with tea alias
-
-Instance settings (tea config set --host <url> <key> <value>):
-  user             active account; change it with tea auth switch
-  ssh_host         SSH host[:port] when it differs from the web host
-  insecure         true skips TLS certificate verification
-  git_protocol     https or ssh, overriding the preference for this instance
-  oauth_client_id  OAuth application used by tea auth login --oauth
-
-Account settings (tea config set --host <url> --user <name> <key> <value>):
-  ssh_key, ssh_agent, ssh_certificate_principal, ssh_key_fingerprint`}
+Preferences: default_host, git_protocol, editor, prompt (enabled or disabled), pager,
+browser (never disables opening), color, hyperlinks and markdown (auto or raw), remote and
+aliases (see tea alias).
+Instance settings (--host <url>): user, ssh_host, insecure, git_protocol, oauth_client_id.
+Account settings (--host <url> --user <name>): ssh_key, ssh_agent,
+ssh_certificate_principal, ssh_key_fingerprint.`}
 	group.AddCommand(&cobra.Command{
 		Use: "path", Short: "Print the paths of the settings files", Args: argsExact(0),
 		Annotations: map[string]string{"tea.text": "config path prints text", "tea.offline": "true"},