Improve test coverage for cmd/bd

- Add comprehensive version mismatch tests (checkVersionMismatch: 25% → 100%)
- Add daemon formatting helper tests (formatDaemonDuration, formatDaemonRelativeTime: 0% → 100%)
- Add auto-import test cases (checkAndAutoImport: 27.8% → 44.4%)
- Add compact eligibility test

Overall coverage: 47.9% → 48.3%
cmd/bd coverage: 20.5% → 21.0%

New test files:
- cmd/bd/autoflush_version_test.go (5 test functions)
- cmd/bd/daemons_test.go (2 test functions)

All tests passing.

Amp-Thread-ID: https://ampcode.com/threads/T-29fa5379-fd71-4f75-bc4f-272beff96c8f
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/daemons_test.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFormatDaemonDuration(t *testing.T) {
+	tests := []struct {
+		name     string
+		seconds  float64
+		expected string
+	}{
+		{"zero", 0, "0s"},
+		{"seconds", 45, "45s"},
+		{"minutes", 90.5, "2m"},
+		{"hours", 3661, "1.0h"},
+		{"days", 86400, "1.0d"},
+		{"mixed", 93784, "1.1d"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := formatDaemonDuration(tt.seconds)
+			if got != tt.expected {
+				t.Errorf("formatDaemonDuration(%f) = %q, want %q", tt.seconds, got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestFormatDaemonRelativeTime(t *testing.T) {
+	tests := []struct {
+		name     string
+		ago      time.Duration
+		expected string
+	}{
+		{"just now", 5 * time.Second, "just now"},
+		{"minutes ago", 3 * time.Minute, "3m ago"},
+		{"hours ago", 2 * time.Hour, "2.0h ago"},
+		{"days ago", 25 * time.Hour, "1.0d ago"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			testTime := time.Now().Add(-tt.ago)
+			got := formatDaemonRelativeTime(testTime)
+			if got != tt.expected {
+				t.Errorf("formatDaemonRelativeTime(%v) = %q, want %q", testTime, got, tt.expected)
+			}
+		})
+	}
+}
+
+// TestDaemonsFormatFunctions tests the formatting helpers
+// Integration tests for the actual commands are in daemon_test.go