Enforce canonical database naming (beads.db) - bd-165

- Added CanonicalDatabaseName constant (beads.db) and LegacyDatabaseNames list
- Updated bd init to use canonical name via constant
- Added daemon validation to reject non-canonical database names
- Updated bd migrate to use canonical name constant
- Enhanced FindDatabasePath to warn when using legacy database names
- All database discovery now prefers beads.db with backward compatibility

Closes bd-165

cmd/bd/daemon.go

@@ -1162,11 +1162,23 @@ func runDaemonLoop(interval time.Duration, autoCommit, autoPush bool, logPath, p
 			for _, db := range validDBs {
 				log.log("  - %s", filepath.Base(db))
 			}
-			log.log("Run 'bd init' to migrate to beads.db or manually remove old databases")
+			log.log("")
+			log.log("Beads requires a single canonical database: %s", beads.CanonicalDatabaseName)
+			log.log("Run 'bd init' to migrate legacy databases")
 			os.Exit(1)
 		}
 	}
 
+	// Validate using canonical name
+	dbBaseName := filepath.Base(daemonDBPath)
+	if dbBaseName != beads.CanonicalDatabaseName {
+		log.log("Error: Non-canonical database name: %s", dbBaseName)
+		log.log("Expected: %s", beads.CanonicalDatabaseName)
+		log.log("")
+		log.log("Run 'bd init' to migrate to canonical name")
+		os.Exit(1)
+	}
+
 	log.log("Using database: %s", daemonDBPath)
 
 	store, err := sqlite.New(daemonDBPath)

cmd/bd/init.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/fatih/color"
 	"github.com/spf13/cobra"
+	"github.com/steveyegge/beads"
 	"github.com/steveyegge/beads/internal/configfile"
 	"github.com/steveyegge/beads/internal/storage/sqlite"
 )
@@ -48,7 +49,7 @@ and database file. Optionally specify a custom issue prefix.`,
 		// Use global dbPath if set via --db flag or BEADS_DB env var, otherwise default to .beads/beads.db
 		initDBPath := dbPath
 		if initDBPath == "" {
-		initDBPath = filepath.Join(".beads", "beads.db")
+		initDBPath = filepath.Join(".beads", beads.CanonicalDatabaseName)
 		}
 
 		// Migrate old database files if they exist

cmd/bd/migrate.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/fatih/color"
 	"github.com/spf13/cobra"
+	"github.com/steveyegge/beads"
 	"github.com/steveyegge/beads/internal/storage/sqlite"
 	_ "modernc.org/sqlite"
 )
@@ -73,7 +74,7 @@ This command:
 		}
 
 		// Check if beads.db exists and is current
-		targetPath := filepath.Join(beadsDir, "beads.db")
+		targetPath := filepath.Join(beadsDir, beads.CanonicalDatabaseName)
 		var currentDB *dbInfo
 		var oldDBs []*dbInfo
 
@@ -271,7 +272,7 @@ This command:
 		if jsonOutput {
 			outputJSON(map[string]interface{}{
 				"status":           "success",
-				"current_database": "beads.db",
+				"current_database": beads.CanonicalDatabaseName,
 				"version":          Version,
 				"migrated":         needsMigration,
 				"version_updated":  needsVersionUpdate,