feat(sync): read sync-branch from config.yaml (bd-io0)

sync.branch config was lost on clone because it was only stored in
the database (which is gitignored). Now syncbranch.Get() checks:
1. BEADS_SYNC_BRANCH env var (highest)
2. config.yaml sync-branch (tracked, persists across clones)
3. Database config (local override)
4. Empty (use current branch)

Changes:
- Update syncbranch.Get() to check config.yaml
- Update config.yaml template with sync-branch option
- Set sync-branch: beads-sync in this repo config.yaml

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

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

.beads/config.yaml

@@ -37,6 +37,11 @@ issue-prefix: "bd"
 # Debounce interval for auto-flush (can also use BEADS_FLUSH_DEBOUNCE)
 # flush-debounce: "5s"
 
+# Git branch for beads commits (bd sync will commit to this branch)
+# IMPORTANT: This setting persists across clones (unlike database config).
+# Can also use BEADS_SYNC_BRANCH env var for local override.
+sync-branch: "beads-sync"
+
 # Integration settings (access with 'bd config get/set')
 # These are stored in the database, not in this file:
 # - jira.url
@@ -45,4 +50,3 @@ issue-prefix: "bd"
 # - linear.api-key
 # - github.org
 # - github.repo
-# - sync.branch - Git branch for beads commits (use BEADS_SYNC_BRANCH env var or bd config set)

cmd/bd/init.go

@@ -1038,6 +1038,13 @@ func createConfigYaml(beadsDir string, noDbMode bool) error {
 # Debounce interval for auto-flush (can also use BEADS_FLUSH_DEBOUNCE)
 # flush-debounce: "5s"
 
+# Git branch for beads commits (bd sync will commit to this branch)
+# IMPORTANT: Set this for team projects so all clones use the same sync branch.
+# This setting persists across clones (unlike database config which is gitignored).
+# Can also use BEADS_SYNC_BRANCH env var for local override.
+# If not set, bd sync will require you to run 'bd config set sync.branch <branch>'.
+# sync-branch: "beads-sync"
+
 # Multi-repo configuration (experimental - bd-307)
 # Allows hydrating from multiple repositories and routing writes to the correct JSONL
 # repos:
@@ -1054,7 +1061,6 @@ func createConfigYaml(beadsDir string, noDbMode bool) error {
 # - linear.api-key
 # - github.org
 # - github.repo
-# - sync.branch - Git branch for beads commits (use BEADS_SYNC_BRANCH env var or bd config set)
 `, noDbLine)
 
 	if err := os.WriteFile(configYamlPath, []byte(configYamlTemplate), 0600); err != nil {

internal/syncbranch/syncbranch.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"regexp"
 
+	"github.com/steveyegge/beads/internal/config"
 	"github.com/steveyegge/beads/internal/storage"
 )
 
@@ -57,10 +58,11 @@ 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 (tracked in git, persists across clones)
+// 3. sync.branch from database config (local override)
+// 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 +70,16 @@ func Get(ctx context.Context, store storage.Storage) (string, error) {
 		return envBranch, nil
 	}
 
-	// Check database config
+	// Check config.yaml (tracked in git, persists across clones)
+	// This is the recommended way to configure sync branch for teams
+	if yamlBranch := config.GetString("sync-branch"); yamlBranch != "" {
+		if err := ValidateBranchName(yamlBranch); err != nil {
+			return "", fmt.Errorf("invalid sync-branch in config.yaml: %w", err)
+		}
+		return yamlBranch, nil
+	}
+
+	// Check database config (local override, doesn't persist across clones)
 	dbBranch, err := store.GetConfig(ctx, ConfigKey)
 	if err != nil {
 		return "", fmt.Errorf("failed to get %s from config: %w", ConfigKey, err)