feat: Auto-migrate database on CLI version bump (bd-jgxi)

When CLI is upgraded (e.g., 0.24.0 → 0.24.1), the database version
is now automatically updated to match the CLI version during
PersistentPreRun. This fixes the recurring UX issue where bd doctor
shows version mismatch after every CLI upgrade.

Implementation:
- Added autoMigrateOnVersionBump() function in version_tracking.go
- Calls after trackBdVersion() in PersistentPreRun
- Best-effort and silent failures to avoid disrupting commands
- Only updates bd_version metadata field
- Includes comprehensive test coverage

Changes:
- cmd/bd/main.go: Call autoMigrateOnVersionBump() in PersistentPreRun
- cmd/bd/version_tracking.go: Implement auto-migration logic
- cmd/bd/version_tracking_test.go: Add tests for auto-migration

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

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

cmd/bd/version_tracking_test.go

@@ -1,11 +1,14 @@
 package main
 
 import (
+	"context"
 	"os"
 	"path/filepath"
 	"testing"
 
+	"github.com/steveyegge/beads/internal/beads"
 	"github.com/steveyegge/beads/internal/configfile"
+	"github.com/steveyegge/beads/internal/storage/sqlite"
 )
 
 func TestGetVersionsSince(t *testing.T) {
@@ -308,3 +311,187 @@ func TestMaybeShowUpgradeNotification(t *testing.T) {
 		t.Error("Should not change acknowledged state on subsequent calls")
 	}
 }
+
+func TestAutoMigrateOnVersionBump_NoUpgrade(t *testing.T) {
+	// Save original state
+	origUpgradeDetected := versionUpgradeDetected
+	defer func() {
+		versionUpgradeDetected = origUpgradeDetected
+	}()
+
+	// Reset state - no upgrade detected
+	versionUpgradeDetected = false
+
+	// Should return early without doing anything
+	autoMigrateOnVersionBump()
+
+	// Test passes if no panic occurs
+}
+
+func TestAutoMigrateOnVersionBump_NoDatabase(t *testing.T) {
+	// Create temp .beads directory without a database
+	tmpDir := t.TempDir()
+	beadsDir := filepath.Join(tmpDir, ".beads")
+	if err := os.MkdirAll(beadsDir, 0755); err != nil {
+		t.Fatalf("Failed to create .beads: %v", err)
+	}
+
+	// Change to temp directory
+	origWd, _ := os.Getwd()
+	defer os.Chdir(origWd)
+	if err := os.Chdir(tmpDir); err != nil {
+		t.Fatalf("Failed to change to temp dir: %v", err)
+	}
+
+	// Create metadata.json
+	cfg := configfile.DefaultConfig()
+	cfg.LastBdVersion = "0.22.0"
+	if err := cfg.Save(beadsDir); err != nil {
+		t.Fatalf("Failed to save config: %v", err)
+	}
+
+	// Save original state
+	origUpgradeDetected := versionUpgradeDetected
+	defer func() {
+		versionUpgradeDetected = origUpgradeDetected
+	}()
+
+	// Simulate version upgrade
+	versionUpgradeDetected = true
+
+	// Should handle gracefully when database doesn't exist
+	autoMigrateOnVersionBump()
+
+	// Test passes if no panic occurs
+}
+
+func TestAutoMigrateOnVersionBump_MigratesVersion(t *testing.T) {
+	// Create temp .beads directory
+	tmpDir := t.TempDir()
+	beadsDir := filepath.Join(tmpDir, ".beads")
+	if err := os.MkdirAll(beadsDir, 0755); err != nil {
+		t.Fatalf("Failed to create .beads: %v", err)
+	}
+
+	// Change to temp directory
+	origWd, _ := os.Getwd()
+	defer os.Chdir(origWd)
+	if err := os.Chdir(tmpDir); err != nil {
+		t.Fatalf("Failed to change to temp dir: %v", err)
+	}
+
+	// Create metadata.json
+	cfg := configfile.DefaultConfig()
+	cfg.LastBdVersion = "0.22.0"
+	if err := cfg.Save(beadsDir); err != nil {
+		t.Fatalf("Failed to save config: %v", err)
+	}
+
+	// Create database with old version
+	dbPath := filepath.Join(beadsDir, beads.CanonicalDatabaseName)
+	ctx := context.Background()
+	store, err := sqlite.New(ctx, dbPath)
+	if err != nil {
+		t.Fatalf("Failed to create database: %v", err)
+	}
+
+	// Set old database version
+	oldVersion := "0.22.0"
+	if err := store.SetMetadata(ctx, "bd_version", oldVersion); err != nil {
+		t.Fatalf("Failed to set old version: %v", err)
+	}
+	_ = store.Close()
+
+	// Save original state
+	origUpgradeDetected := versionUpgradeDetected
+	defer func() {
+		versionUpgradeDetected = origUpgradeDetected
+	}()
+
+	// Simulate version upgrade
+	versionUpgradeDetected = true
+
+	// Call auto-migration
+	autoMigrateOnVersionBump()
+
+	// Verify database version was updated
+	store, err = sqlite.New(ctx, dbPath)
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer store.Close()
+
+	newVersion, err := store.GetMetadata(ctx, "bd_version")
+	if err != nil {
+		t.Fatalf("Failed to read database version: %v", err)
+	}
+
+	if newVersion != Version {
+		t.Errorf("Database version not updated: got %q, want %q", newVersion, Version)
+	}
+}
+
+func TestAutoMigrateOnVersionBump_AlreadyMigrated(t *testing.T) {
+	// Create temp .beads directory
+	tmpDir := t.TempDir()
+	beadsDir := filepath.Join(tmpDir, ".beads")
+	if err := os.MkdirAll(beadsDir, 0755); err != nil {
+		t.Fatalf("Failed to create .beads: %v", err)
+	}
+
+	// Change to temp directory
+	origWd, _ := os.Getwd()
+	defer os.Chdir(origWd)
+	if err := os.Chdir(tmpDir); err != nil {
+		t.Fatalf("Failed to change to temp dir: %v", err)
+	}
+
+	// Create metadata.json
+	cfg := configfile.DefaultConfig()
+	cfg.LastBdVersion = Version
+	if err := cfg.Save(beadsDir); err != nil {
+		t.Fatalf("Failed to save config: %v", err)
+	}
+
+	// Create database with current version
+	dbPath := filepath.Join(beadsDir, beads.CanonicalDatabaseName)
+	ctx := context.Background()
+	store, err := sqlite.New(ctx, dbPath)
+	if err != nil {
+		t.Fatalf("Failed to create database: %v", err)
+	}
+
+	// Set current database version
+	if err := store.SetMetadata(ctx, "bd_version", Version); err != nil {
+		t.Fatalf("Failed to set version: %v", err)
+	}
+	_ = store.Close()
+
+	// Save original state
+	origUpgradeDetected := versionUpgradeDetected
+	defer func() {
+		versionUpgradeDetected = origUpgradeDetected
+	}()
+
+	// Simulate version upgrade
+	versionUpgradeDetected = true
+
+	// Call auto-migration - should be a no-op
+	autoMigrateOnVersionBump()
+
+	// Verify database version is still current
+	store, err = sqlite.New(ctx, dbPath)
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer store.Close()
+
+	currentVersion, err := store.GetMetadata(ctx, "bd_version")
+	if err != nil {
+		t.Fatalf("Failed to read database version: %v", err)
+	}
+
+	if currentVersion != Version {
+		t.Errorf("Database version changed unexpectedly: got %q, want %q", currentVersion, Version)
+	}
+}