feat(ui): add elapsed timer to nest progress form

Show a live elapsed-time counter that updates every second during
nesting. Rename "Remnant" label to "Unused" for clarity.

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

OpenNest/Forms/NestProgressForm.Designer.cs

@@ -39,6 +39,8 @@ namespace OpenNest.Forms
             this.densityValue = new System.Windows.Forms.Label();
             this.remnantLabel = new System.Windows.Forms.Label();
             this.remnantValue = new System.Windows.Forms.Label();
+            this.elapsedLabel = new System.Windows.Forms.Label();
+            this.elapsedValue = new System.Windows.Forms.Label();
             this.stopButton = new System.Windows.Forms.Button();
             this.buttonPanel = new System.Windows.Forms.FlowLayoutPanel();
             this.table.SuspendLayout();
@@ -60,18 +62,21 @@ namespace OpenNest.Forms
             this.table.Controls.Add(this.densityValue, 1, 3);
             this.table.Controls.Add(this.remnantLabel, 0, 4);
             this.table.Controls.Add(this.remnantValue, 1, 4);
+            this.table.Controls.Add(this.elapsedLabel, 0, 5);
+            this.table.Controls.Add(this.elapsedValue, 1, 5);
             this.table.Dock = System.Windows.Forms.DockStyle.Top;
             this.table.Location = new System.Drawing.Point(0, 0);
             this.table.Name = "table";
             this.table.Padding = new System.Windows.Forms.Padding(8);
-            this.table.RowCount = 5;
+            this.table.RowCount = 6;
+            this.table.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.AutoSize));
             this.table.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.AutoSize));
             this.table.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.AutoSize));
             this.table.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.AutoSize));
             this.table.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.AutoSize));
             this.table.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.AutoSize));
             this.table.AutoSize = true;
-            this.table.Size = new System.Drawing.Size(264, 130);
+            this.table.Size = new System.Drawing.Size(264, 156);
             this.table.TabIndex = 0;
             //
             // phaseLabel
@@ -140,7 +145,7 @@ namespace OpenNest.Forms
             this.remnantLabel.Font = new System.Drawing.Font(System.Drawing.SystemFonts.DefaultFont, System.Drawing.FontStyle.Bold);
             this.remnantLabel.Margin = new System.Windows.Forms.Padding(4);
             this.remnantLabel.Name = "remnantLabel";
-            this.remnantLabel.Text = "Remnant:";
+            this.remnantLabel.Text = "Unused:";
             //
             // remnantValue
             //
@@ -149,6 +154,21 @@ namespace OpenNest.Forms
             this.remnantValue.Name = "remnantValue";
             this.remnantValue.Text = "\u2014";
             //
+            // elapsedLabel
+            //
+            this.elapsedLabel.AutoSize = true;
+            this.elapsedLabel.Font = new System.Drawing.Font(System.Drawing.SystemFonts.DefaultFont, System.Drawing.FontStyle.Bold);
+            this.elapsedLabel.Margin = new System.Windows.Forms.Padding(4);
+            this.elapsedLabel.Name = "elapsedLabel";
+            this.elapsedLabel.Text = "Elapsed:";
+            //
+            // elapsedValue
+            //
+            this.elapsedValue.AutoSize = true;
+            this.elapsedValue.Margin = new System.Windows.Forms.Padding(4);
+            this.elapsedValue.Name = "elapsedValue";
+            this.elapsedValue.Text = "0:00";
+            //
             // stopButton
             //
             this.stopButton.Anchor = System.Windows.Forms.AnchorStyles.None;
@@ -174,7 +194,7 @@ namespace OpenNest.Forms
             //
             this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
             this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
-            this.ClientSize = new System.Drawing.Size(264, 181);
+            this.ClientSize = new System.Drawing.Size(264, 207);
             this.Controls.Add(this.buttonPanel);
             this.Controls.Add(this.table);
             this.Controls.SetChildIndex(this.table, 0);
@@ -206,6 +226,8 @@ namespace OpenNest.Forms
         private System.Windows.Forms.Label densityValue;
         private System.Windows.Forms.Label remnantLabel;
         private System.Windows.Forms.Label remnantValue;
+        private System.Windows.Forms.Label elapsedLabel;
+        private System.Windows.Forms.Label elapsedValue;
         private System.Windows.Forms.Button stopButton;
         private System.Windows.Forms.FlowLayoutPanel buttonPanel;
     }

OpenNest/Forms/NestProgressForm.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using System.Threading;
 using System.Windows.Forms;
 
@@ -7,6 +8,8 @@ namespace OpenNest.Forms
     public partial class NestProgressForm : Form
     {
         private readonly CancellationTokenSource cts;
+        private readonly Stopwatch stopwatch = Stopwatch.StartNew();
+        private readonly System.Windows.Forms.Timer elapsedTimer;
 
         public NestProgressForm(CancellationTokenSource cts, bool showPlateRow = true)
         {
@@ -18,6 +21,10 @@ namespace OpenNest.Forms
                 plateLabel.Visible = false;
                 plateValue.Visible = false;
             }
+
+            elapsedTimer = new System.Windows.Forms.Timer { Interval = 1000 };
+            elapsedTimer.Tick += (s, e) => UpdateElapsed();
+            elapsedTimer.Start();
         }
 
         public void UpdateProgress(NestProgress progress)
@@ -37,6 +44,10 @@ namespace OpenNest.Forms
             if (IsDisposed || !IsHandleCreated)
                 return;
 
+            stopwatch.Stop();
+            elapsedTimer.Stop();
+            UpdateElapsed();
+
             phaseValue.Text = "Done";
             stopButton.Text = "Close";
             stopButton.Enabled = true;
@@ -44,6 +55,17 @@ namespace OpenNest.Forms
             stopButton.Click += (s, e) => Close();
         }
 
+        private void UpdateElapsed()
+        {
+            if (IsDisposed || !IsHandleCreated)
+                return;
+
+            var elapsed = stopwatch.Elapsed;
+            elapsedValue.Text = elapsed.TotalHours >= 1
+                ? elapsed.ToString(@"h\:mm\:ss")
+                : elapsed.ToString(@"m\:ss");
+        }
+
         private void StopButton_Click(object sender, EventArgs e)
         {
             cts.Cancel();
@@ -53,6 +75,10 @@ namespace OpenNest.Forms
 
         protected override void OnFormClosing(FormClosingEventArgs e)
         {
+            elapsedTimer.Stop();
+            elapsedTimer.Dispose();
+            stopwatch.Stop();
+
             if (!cts.IsCancellationRequested)
                 cts.Cancel();