Add explicit working folder; rename project from CadSearchGui to PrepStep

Working folder (phase 1): CSV/raw/step/step_finali all used to live split
across two different implicit locations (CSV in the "repo root" found by
walking up for CLAUDE.md, raw/step next to the input distinta file) with
neither shown to the user. That repo-root lookup also silently breaks once
the app runs as a standalone published exe on a machine with no repo/
CLAUDE.md at all. Replaced both with one explicit "cartella di lavoro",
auto-suggested (last used, remembered the same way as the DB path) and
changeable from phase 1, with no dependency on any repo marker file.

Rename: CadSearchGui was the working name from before the app had a
product identity; renamed folders, csproj files, namespace and the
AppData settings folder to PrepStep throughout, matching the exe name
already in use. Product-facing name stays "Cevolani StepPrep".

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

PrepStep/ReportCompletezzaForm.cs

@@ -0,0 +1,61 @@
+namespace PrepStep;
+
+/// <summary>Mostra, per ogni assieme della distinta base, se tutti i suoi componenti
+/// (ricorsivamente fino ai PRT) sono presenti nell'indice (v) o mancano (x).</summary>
+public class ReportCompletezzaForm : Form
+{
+    public ReportCompletezzaForm(List<(string Componente, string Descrizione, bool? Completo)> righe)
+    {
+        int completi = righe.Count(r => r.Completo == true);
+        int incompleti = righe.Count(r => r.Completo == false);
+        int nonTrovati = righe.Count(r => r.Completo is null);
+
+        Text = "Completezza assiemi";
+        ClientSize = new Size(720, 440);
+        StartPosition = FormStartPosition.CenterParent;
+        Font = new Font("Segoe UI", 9.5f);
+
+        var lblInfo = new Label
+        {
+            Dock = DockStyle.Top,
+            AutoSize = true,
+            Padding = new Padding(12, 8, 12, 8),
+            Text = $"{completi} completi, {incompleti} incompleti, {nonTrovati} non trovati nell'indice "
+                 + $"su {righe.Count} componenti. Nota: la scansione dei .asm è euristica, qualche "
+                 + "falso 'incompleto' è possibile.",
+        };
+
+        var grid = new DataGridView
+        {
+            Dock = DockStyle.Fill,
+            ReadOnly = true,
+            AllowUserToAddRows = false,
+            AllowUserToDeleteRows = false,
+            RowHeadersVisible = false,
+            SelectionMode = DataGridViewSelectionMode.FullRowSelect,
+            AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill,
+        };
+        grid.Columns.Add("componente", "Componente");
+        grid.Columns.Add("descrizione", "Descrizione");
+        grid.Columns.Add("completo", "Completo");
+        grid.Columns["componente"]!.FillWeight = 20;
+        grid.Columns["descrizione"]!.FillWeight = 55;
+        grid.Columns["completo"]!.FillWeight = 25;
+
+        foreach (var (componente, descrizione, completo) in righe.OrderBy(r => r.Completo).ThenBy(r => r.Componente))
+        {
+            string testo = completo switch { true => "✓", false => "✗", null => "?" };
+            int i = grid.Rows.Add(componente, descrizione, testo);
+            grid.Rows[i].DefaultCellStyle.ForeColor = completo switch
+            {
+                true => Color.DarkGreen,
+                false => Color.DarkRed,
+                null => Color.Gray,
+            };
+            grid.Rows[i].Cells["completo"].Style.Alignment = DataGridViewContentAlignment.MiddleCenter;
+        }
+
+        Controls.Add(grid);
+        Controls.Add(lblInfo);
+    }
+}