refactor: extract training data collection into OpenNest.Training

Move brute-force data collection, TrainingDatabase, and GPU init from
OpenNest.Console into a dedicated OpenNest.Training project. Replaces
raw Microsoft.Data.Sqlite with EF Core. Console is now a pure nesting
CLI with template support and cleaned-up usage output.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Training/Data/TrainingDbContext.cs

@@ -0,0 +1,38 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace OpenNest.Training.Data
+{
+    public class TrainingDbContext : DbContext
+    {
+        public DbSet<TrainingPart> Parts { get; set; }
+        public DbSet<TrainingRun> Runs { get; set; }
+
+        private readonly string _dbPath;
+
+        public TrainingDbContext(string dbPath)
+        {
+            _dbPath = dbPath;
+        }
+
+        protected override void OnConfiguring(DbContextOptionsBuilder options)
+        {
+            options.UseSqlite($"Data Source={_dbPath}");
+        }
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<TrainingPart>(e =>
+            {
+                e.HasIndex(p => p.FileName).HasDatabaseName("idx_parts_filename");
+            });
+
+            modelBuilder.Entity<TrainingRun>(e =>
+            {
+                e.HasIndex(r => r.PartId).HasDatabaseName("idx_runs_partid");
+                e.HasOne(r => r.Part)
+                    .WithMany(p => p.Runs)
+                    .HasForeignKey(r => r.PartId);
+            });
+        }
+    }
+}

OpenNest.Training/Data/TrainingPart.cs

@@ -0,0 +1,28 @@
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace OpenNest.Training.Data
+{
+    [Table("Parts")]
+    public class TrainingPart
+    {
+        [Key]
+        public long Id { get; set; }
+
+        [MaxLength(260)]
+        public string FileName { get; set; }
+
+        public double Area { get; set; }
+        public double Convexity { get; set; }
+        public double AspectRatio { get; set; }
+        public double BBFill { get; set; }
+        public double Circularity { get; set; }
+        public double PerimeterToAreaRatio { get; set; }
+        public int VertexCount { get; set; }
+        public byte[] Bitmask { get; set; }
+        public string GeometryData { get; set; }
+
+        public List<TrainingRun> Runs { get; set; } = new();
+    }
+}

OpenNest.Training/Data/TrainingRun.cs

@@ -0,0 +1,25 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace OpenNest.Training.Data
+{
+    [Table("Runs")]
+    public class TrainingRun
+    {
+        [Key]
+        public long Id { get; set; }
+
+        public long PartId { get; set; }
+        public double SheetWidth { get; set; }
+        public double SheetHeight { get; set; }
+        public double Spacing { get; set; }
+        public int PartCount { get; set; }
+        public double Utilization { get; set; }
+        public long TimeMs { get; set; }
+        public string LayoutData { get; set; }
+        public string FilePath { get; set; }
+
+        [ForeignKey(nameof(PartId))]
+        public TrainingPart Part { get; set; }
+    }
+}