feat: auto-detect non-TTY and adjust output (bd-xrwy)

Add TTY detection to automatically disable ANSI colors when stdout is
piped or redirected. Respects standard conventions:
- NO_COLOR environment variable (no-color.org)
- CLICOLOR=0 disables color
- CLICOLOR_FORCE enables color even in non-TTY

Also adds ShouldUseEmoji() helper controlled by BD_NO_EMOJI.
Pager already disabled non-TTY in previous work (bd-jdz3).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/ui/styles.go

@@ -7,8 +7,16 @@ import (
 	"strings"
 
 	"github.com/charmbracelet/lipgloss"
+	"github.com/muesli/termenv"
 )
 
+func init() {
+	// Disable colors when not appropriate (non-TTY, NO_COLOR, etc.)
+	if !ShouldUseColor() {
+		lipgloss.SetColorProfile(termenv.Ascii)
+	}
+}
+
 // Ayu theme color palette
 // Dark: https://terminalcolors.com/themes/ayu/dark/
 // Light: https://terminalcolors.com/themes/ayu/light/

internal/ui/terminal.go

@@ -0,0 +1,52 @@
+// Package ui provides terminal styling and output helpers for beads CLI.
+package ui
+
+import (
+	"os"
+
+	"golang.org/x/term"
+)
+
+// IsTerminal returns true if stdout is connected to a terminal (TTY).
+func IsTerminal() bool {
+	return term.IsTerminal(int(os.Stdout.Fd()))
+}
+
+// ShouldUseColor determines if ANSI color codes should be used.
+// Respects standard conventions:
+//   - NO_COLOR: https://no-color.org/ - disables color if set
+//   - CLICOLOR=0: disables color
+//   - CLICOLOR_FORCE: forces color even in non-TTY
+//   - Falls back to TTY detection
+func ShouldUseColor() bool {
+	// NO_COLOR standard - any value disables color
+	if os.Getenv("NO_COLOR") != "" {
+		return false
+	}
+
+	// CLICOLOR=0 disables color
+	if os.Getenv("CLICOLOR") == "0" {
+		return false
+	}
+
+	// CLICOLOR_FORCE forces color even in non-TTY
+	if os.Getenv("CLICOLOR_FORCE") != "" {
+		return true
+	}
+
+	// Default: use color only if stdout is a TTY
+	return IsTerminal()
+}
+
+// ShouldUseEmoji determines if emoji decorations should be used.
+// Disabled in non-TTY mode to keep output machine-readable.
+// Can be controlled with BD_NO_EMOJI environment variable.
+func ShouldUseEmoji() bool {
+	// Explicit disable
+	if os.Getenv("BD_NO_EMOJI") != "" {
+		return false
+	}
+
+	// Default: use emoji only if stdout is a TTY
+	return IsTerminal()
+}

internal/ui/terminal_test.go

@@ -0,0 +1,139 @@
+package ui
+
+import (
+	"os"
+	"testing"
+)
+
+func TestShouldUseColor(t *testing.T) {
+	// Save original env vars
+	origNoColor := os.Getenv("NO_COLOR")
+	origCliColor := os.Getenv("CLICOLOR")
+	origCliColorForce := os.Getenv("CLICOLOR_FORCE")
+	defer func() {
+		setEnv("NO_COLOR", origNoColor)
+		setEnv("CLICOLOR", origCliColor)
+		setEnv("CLICOLOR_FORCE", origCliColorForce)
+	}()
+
+	tests := []struct {
+		name            string
+		noColor         string
+		cliColor        string
+		cliColorForce   string
+		wantColor       bool
+		skipTTYDepCheck bool // Some tests don't depend on TTY state
+	}{
+		{
+			name:            "NO_COLOR disables color",
+			noColor:         "1",
+			wantColor:       false,
+			skipTTYDepCheck: true,
+		},
+		{
+			name:            "NO_COLOR empty string value still disables",
+			noColor:         "", // will be unset
+			cliColor:        "",
+			cliColorForce:   "",
+			wantColor:       false, // depends on TTY, but we're in test = no TTY
+			skipTTYDepCheck: false,
+		},
+		{
+			name:            "CLICOLOR=0 disables color",
+			cliColor:        "0",
+			wantColor:       false,
+			skipTTYDepCheck: true,
+		},
+		{
+			name:            "CLICOLOR_FORCE enables color even in non-TTY",
+			cliColorForce:   "1",
+			wantColor:       true,
+			skipTTYDepCheck: true,
+		},
+		{
+			name:            "NO_COLOR takes precedence over CLICOLOR_FORCE",
+			noColor:         "1",
+			cliColorForce:   "1",
+			wantColor:       false,
+			skipTTYDepCheck: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Clear all vars first
+			os.Unsetenv("NO_COLOR")
+			os.Unsetenv("CLICOLOR")
+			os.Unsetenv("CLICOLOR_FORCE")
+
+			// Set test-specific vars
+			if tt.noColor != "" {
+				os.Setenv("NO_COLOR", tt.noColor)
+			}
+			if tt.cliColor != "" {
+				os.Setenv("CLICOLOR", tt.cliColor)
+			}
+			if tt.cliColorForce != "" {
+				os.Setenv("CLICOLOR_FORCE", tt.cliColorForce)
+			}
+
+			got := ShouldUseColor()
+			if tt.skipTTYDepCheck && got != tt.wantColor {
+				t.Errorf("ShouldUseColor() = %v, want %v", got, tt.wantColor)
+			}
+		})
+	}
+}
+
+func TestShouldUseEmoji(t *testing.T) {
+	// Save original env var
+	origNoEmoji := os.Getenv("BD_NO_EMOJI")
+	defer setEnv("BD_NO_EMOJI", origNoEmoji)
+
+	tests := []struct {
+		name      string
+		noEmoji   string
+		wantEmoji bool
+	}{
+		{
+			name:      "BD_NO_EMOJI disables emoji",
+			noEmoji:   "1",
+			wantEmoji: false,
+		},
+		{
+			name:      "No BD_NO_EMOJI falls back to TTY check",
+			noEmoji:   "",
+			wantEmoji: false, // In test, stdout is not a TTY
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			os.Unsetenv("BD_NO_EMOJI")
+			if tt.noEmoji != "" {
+				os.Setenv("BD_NO_EMOJI", tt.noEmoji)
+			}
+
+			got := ShouldUseEmoji()
+			if got != tt.wantEmoji {
+				t.Errorf("ShouldUseEmoji() = %v, want %v", got, tt.wantEmoji)
+			}
+		})
+	}
+}
+
+func TestIsTerminal(t *testing.T) {
+	// When running under go test, stdout is typically not a TTY
+	got := IsTerminal()
+	// We can't easily assert the value, but we can verify it doesn't panic
+	t.Logf("IsTerminal() = %v (expected false in test environment)", got)
+}
+
+// setEnv sets or unsets an environment variable
+func setEnv(key, value string) {
+	if value == "" {
+		os.Unsetenv(key)
+	} else {
+		os.Setenv(key, value)
+	}
+}