fix(config): print only the value of config get and add display preferences

tea config get printed "key<TAB>value", so $(tea config get editor) was
not usable; it now prints the value alone, and --show-source appends the
source (D18). config get reads the instance's user, and instance settings
come from the selected instance (--host, TEA_HOST, default_host or the
sole instance). Unknown keys list the valid ones, and keys that need
--host or --user say so. config path no longer loads the settings, so it
works when hosts.yml is broken. config list is a table on a terminal.
config set confirms the change on a terminal and warns when default_host
has no account.

config.yml stores the hyperlinks (auto, always, never) and markdown
(auto, raw) preferences that tables and views now read, instead of the
TEA_HYPERLINKS and TEA_MARKDOWN variables. The environment table moves
out of tea config --help into tea help environment.

alias set refuses to replace an alias without --clobber, drops a leading
"tea", and explains how to quote an expansion with spaces or flags.
alias delete takes several names or --all, alias list is a table, and
an empty list says so on a terminal.

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

internal/settings/store.go

@@ -52,6 +52,8 @@ type Preferences struct {
 	Pager       string            `yaml:"pager,omitempty" json:"pager"`
 	Browser     string            `yaml:"browser,omitempty" json:"browser"`
 	Color       string            `yaml:"color,omitempty" json:"color"`
+	Hyperlinks  string            `yaml:"hyperlinks,omitempty" json:"hyperlinks"`
+	Markdown    string            `yaml:"markdown,omitempty" json:"markdown"`
 	Remote      string            `yaml:"remote,omitempty" json:"remote"`
 	Aliases     map[string]string `yaml:"aliases,omitempty" json:"aliases"`
 }
@@ -114,7 +116,7 @@ func New(dir string) *Store {
 
 // Defaults returns a fresh preferences value with built-in settings.
 func Defaults() Preferences {
-	return Preferences{Version: Version, GitProtocol: "https", Prompt: "enabled", Color: "auto", Aliases: map[string]string{}}
+	return Preferences{Version: Version, GitProtocol: "https", Prompt: "enabled", Color: "auto", Hyperlinks: "auto", Markdown: "auto", Aliases: map[string]string{}}
 }
 
 // stored omits built-in defaults so that only explicit settings are persisted.
@@ -129,6 +131,12 @@ func (p Preferences) stored() Preferences {
 	if p.Color == defaults.Color {
 		p.Color = ""
 	}
+	if p.Hyperlinks == defaults.Hyperlinks {
+		p.Hyperlinks = ""
+	}
+	if p.Markdown == defaults.Markdown {
+		p.Markdown = ""
+	}
 	return p
 }
 
@@ -247,6 +255,12 @@ func (s Snapshot) Validate() error {
 	if p.Color != "auto" && p.Color != "always" && p.Color != "never" {
 		return errors.New("color must be auto, always, or never")
 	}
+	if p.Hyperlinks != "auto" && p.Hyperlinks != "always" && p.Hyperlinks != "never" {
+		return errors.New("hyperlinks must be auto, always, or never")
+	}
+	if p.Markdown != "auto" && p.Markdown != "raw" {
+		return errors.New("markdown must be auto or raw")
+	}
 	if p.DefaultHost != "" {
 		normalized, err := NormalizeHost(p.DefaultHost)
 		if err != nil || normalized != p.DefaultHost {