fix: wire up Convert button Click handler (was never attached)

GUI:
- Attach Click event handlers to browse input/output buttons (were defined but never wired up)
- Remove ReadOnly=true from input/output text boxes so users can type or copy paths

CLI:
- Make Cli.Run return bool to signal errors
- Only pause with Console.ReadLine() when an error occurs (not on success)
- Fix default case to return true

Core:
- Add System.Text.Encoding.CodePages package for CP1252 SRT file support
- Call Encoding.RegisterProvider(CodePagesEncodingProvider.Instance) before reading files

ConvertSRTto3DASS.Cli/Cli.cs

@@ -4,19 +4,19 @@ namespace ConvertSRTto3DASS;
 
 internal static class Cli
 {
-    public static void Run(string[] args)
+    public static bool Run(string[] args)
     {
         if (args.Length == 0 || args[0] is "--help" or "-h" or "/?")
         {
             PrintUsage();
-            return;
+            return false;
         }
 
         var inputPath = args[0];
         if (!File.Exists(inputPath))
         {
             Console.Error.WriteLine($"Input file not found: {inputPath}");
-            return;
+            return true;
         }
 
         // Parse options
@@ -80,7 +80,7 @@ internal static class Cli
                     break;
                 default:
                     Console.Error.WriteLine($"Unknown argument: {args[i]}");
-                    return;
+                    return true;
             }
             i++;
         }
@@ -106,11 +106,13 @@ internal static class Cli
             var result = SrtConverter.Convert(options);
             Console.WriteLine($"Parsed:           {result.SubtitleCount} subtitle blocks");
             Console.WriteLine("Conversion complete.");
+            return false;
         }
         catch (Exception ex)
         {
             Console.Error.WriteLine($"ERROR: {ex.Message}");
             Console.Error.WriteLine(ex.ToString());
+            return true;
         }
 
         string GetNextArg(int index) => index + 1 < args.Length ? args[index + 1] : throw new ArgumentException($"Missing value for {args[index]}");

ConvertSRTto3DASS.Cli/ConvertSRTto3DASS.Cli.csproj

@@ -13,6 +13,9 @@
 
   <PropertyGroup Condition="'$(Configuration)' == 'Release'">
     <Optimize>true</Optimize>
+    <PublishSingleFile>true</PublishSingleFile>
+    <PublishReadyToRun>false</PublishReadyToRun>
+    <StripSymbols>true</StripSymbols>
   </PropertyGroup>
 
   <ItemGroup>

ConvertSRTto3DASS.Cli/Program.cs

@@ -2,5 +2,10 @@ namespace ConvertSRTto3DASS;
 
 internal static class Program
 {
-    static void Main(string[] args) => Cli.Run(args);
+    static void Main(string[] args)
+    {
+        var hadError = Cli.Run(args);
+        if (hadError)
+            Console.ReadLine();
+    }
 }

ConvertSRTto3DASS.Core/ConvertSRTto3DASS.Core.csproj

@@ -9,6 +9,10 @@
     <RootNamespace>ConvertSRTto3DASS</RootNamespace>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="System.Text.Encoding.CodePages" Version="8.0.0" />
+  </ItemGroup>
+
   <PropertyGroup Condition="'$(Configuration)' == 'Release'">
     <Optimize>true</Optimize>
   </PropertyGroup>

ConvertSRTto3DASS.Core/SrtConverter.cs

@@ -16,6 +16,9 @@ public static class SrtConverter
 
     public static ConversionResult Convert(ConversionOptions options)
     {
+        // Register legacy codepage support (needed for CP1252, etc.)
+        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+
         var srtText = ReadSrt(options.InputPath);
         var subtitles = ParseSrt(srtText);
         var header = CreateHeader(options);

ConvertSRTto3DASS.Gui/Form1.Designer.cs

@@ -71,11 +71,13 @@ partial class Form1
             Size = new Size(1040, 80)
         };
         label_InputFile = new Label { Text = "Input SRT:", Font = segoe, Location = new Point(15, 25), AutoSize = true };
-        textBox_InputFile = new TextBox { Location = new Point(100, 22), Size = new Size(780, 23), ReadOnly = true };
+        textBox_InputFile = new TextBox { Location = new Point(100, 22), Size = new Size(780, 23) };
         button_BrowseInput = new Button { Text = "Browse...", Location = new Point(890, 20), Size = new Size(90, 25), Font = segoe, FlatStyle = FlatStyle.Flat };
+        button_BrowseInput.Click += button_BrowseInput_Click;
         label_OutputFile = new Label { Text = "Output ASS:", Font = segoe, Location = new Point(15, 55), AutoSize = true };
-        textBox_OutputFile = new TextBox { Location = new Point(100, 52), Size = new Size(780, 23), ReadOnly = true };
+        textBox_OutputFile = new TextBox { Location = new Point(100, 52), Size = new Size(780, 23) };
         button_BrowseOutput = new Button { Text = "Browse...", Location = new Point(890, 50), Size = new Size(90, 25), Font = segoe, FlatStyle = FlatStyle.Flat };
+        button_BrowseOutput.Click += button_BrowseOutput_Click;
         groupBox_File.Controls.AddRange([label_InputFile, textBox_InputFile, button_BrowseInput, label_OutputFile, textBox_OutputFile, button_BrowseOutput]);
 
         // ---- Mode section ----
@@ -95,6 +97,7 @@ partial class Form1
             DropDownStyle = ComboBoxStyle.DropDownList
         };
         comboBox_Mode.Items.AddRange(["SBS (Side-by-Side)", "OU (Over-Under)", "RG (Red-Green)"]);
+        comboBox_Mode.SelectedIndexChanged += comboBox_Mode_SelectedIndexChanged;
         groupBox_Mode.Controls.AddRange([label_Mode, comboBox_Mode]);
 
         // ---- Resolution section ----
@@ -165,6 +168,7 @@ partial class Form1
             ForeColor = Color.White,
             FlatAppearance = { BorderSize = 0 }
         };
+        button_Convert.Click += button_Convert_Click;
 
         // ---- Status ----
         textBox_Status = new TextBox