feat(config): move sync-branch to config.yaml as source of truth

Previously sync.branch was stored in the database via bd config set.
Now it is in config.yaml (version controlled, shared across clones):

  sync-branch: "beads-sync"

Changes:
- Add sync-branch to .beads/config.yaml
- Update syncbranch.Get() to check config.yaml before database
- Add syncbranch.GetFromYAML() and IsConfigured() for fast checks
- Update hooks to read sync-branch from config.yaml directly
- Update bd doctor to check config.yaml instead of database
- Remove auto-fix (config.yaml changes should be committed)

Precedence: BEADS_SYNC_BRANCH env > config.yaml > database (legacy)

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

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

internal/syncbranch/syncbranch.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"regexp"
 
+	"github.com/steveyegge/beads/internal/config"
 	"github.com/steveyegge/beads/internal/storage"
 )
 
@@ -13,6 +14,9 @@ const (
 	// ConfigKey is the database config key for sync branch
 	ConfigKey = "sync.branch"
 
+	// ConfigYAMLKey is the config.yaml key for sync branch
+	ConfigYAMLKey = "sync-branch"
+
 	// EnvVar is the environment variable for sync branch
 	EnvVar = "BEADS_SYNC_BRANCH"
 )
@@ -57,10 +61,11 @@ func ValidateBranchName(name string) error {
 
 // Get retrieves the sync branch configuration with the following precedence:
 // 1. BEADS_SYNC_BRANCH environment variable
-// 2. sync.branch from database config
-// 3. Empty string (meaning use current branch)
+// 2. sync-branch from config.yaml (version controlled, shared across clones)
+// 3. sync.branch from database config (legacy, for backward compatibility)
+// 4. Empty string (meaning use current branch)
 func Get(ctx context.Context, store storage.Storage) (string, error) {
-	// Check environment variable first
+	// Check environment variable first (highest priority)
 	if envBranch := os.Getenv(EnvVar); envBranch != "" {
 		if err := ValidateBranchName(envBranch); err != nil {
 			return "", fmt.Errorf("invalid %s: %w", EnvVar, err)
@@ -68,7 +73,15 @@ func Get(ctx context.Context, store storage.Storage) (string, error) {
 		return envBranch, nil
 	}
 
-	// Check database config
+	// Check config.yaml (version controlled, shared across clones)
+	if yamlBranch := config.GetString(ConfigYAMLKey); yamlBranch != "" {
+		if err := ValidateBranchName(yamlBranch); err != nil {
+			return "", fmt.Errorf("invalid %s in config.yaml: %w", ConfigYAMLKey, err)
+		}
+		return yamlBranch, nil
+	}
+
+	// Check database config (legacy, for backward compatibility)
 	dbBranch, err := store.GetConfig(ctx, ConfigKey)
 	if err != nil {
 		return "", fmt.Errorf("failed to get %s from config: %w", ConfigKey, err)
@@ -83,6 +96,23 @@ func Get(ctx context.Context, store storage.Storage) (string, error) {
 	return dbBranch, nil
 }
 
+// GetFromYAML retrieves sync branch from config.yaml only (no database lookup).
+// This is useful for hooks and checks that need to know if sync-branch is configured
+// in the version-controlled config without database access.
+func GetFromYAML() string {
+	// Check environment variable first
+	if envBranch := os.Getenv(EnvVar); envBranch != "" {
+		return envBranch
+	}
+	return config.GetString(ConfigYAMLKey)
+}
+
+// IsConfigured returns true if sync-branch is configured in config.yaml or env var.
+// This is a fast check that doesn't require database access.
+func IsConfigured() bool {
+	return GetFromYAML() != ""
+}
+
 // Set stores the sync branch configuration in the database
 func Set(ctx context.Context, store storage.Storage, branch string) error {
 	if err := ValidateBranchName(branch); err != nil {