Fix bd-144: Update main .db file timestamp after import (WAL mode)

- Added CheckpointWAL method to SQLite storage
- Import now checkpoints WAL after completion
- Updates main .db file modification time for staleness detection
- PRAGMA wal_checkpoint(FULL) flushes WAL to main database

cmd/bd/import_shared.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"os"
 	"sort"
 	"strings"
 
@@ -242,6 +243,13 @@ func importIssuesCore(ctx context.Context, dbPath string, store storage.Storage,
 		return nil, err
 	}
 
+	// Phase 8: Checkpoint WAL to update main .db file timestamp
+	// This ensures staleness detection sees the database as fresh
+	if err := sqliteStore.CheckpointWAL(ctx); err != nil {
+		// Non-fatal - just log warning
+		fmt.Fprintf(os.Stderr, "Warning: failed to checkpoint WAL: %v\n", err)
+	}
+
 	return result, nil
 }