Handle non existent commands during development (#214)

Currently, when `freestanding` is set to `true` and you try to use a
command which is not registered the bot will throw an exception. (I've
used the `modlogs` command for testing)

This PR fixes that by adding a missing return statement.

As a small improvement to this, i've also added a response to whenever a
command has not been registered which can help during development.

### Context:
```
🛑 [2026.03.17 20:18:25.763] [error] TypeError: Cannot read properties of undefined (reading 'options')
    at CommandHandler.handle_slash_comand (file:///D:/dev/wheatley/build/src/command-handler.js:157:28)
    at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
    at async CommandHandler.on_interaction (file:///D:/dev/wheatley/build/src/command-handler.js:331:17)
Error
  TypeError: Cannot read properties of undefined (reading 'options')
      at CommandHandler.handle_slash_comand (file:///D:/dev/wheatley/build/src/command-handler.js:157:28)
      at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
      at async CommandHandler.on_interaction (file:///D:/dev/wheatley/build/src/command-handler.js:331:17)
  Trace
      at M.error (file:///D:/dev/wheatley/build/src/utils/debugging-and-logging.js:61:17)
      at Wheatley.critical_error (file:///D:/dev/wheatley/build/src/wheatley.js:229:15)
      at CommandHandler.on_interaction (file:///D:/dev/wheatley/build/src/command-handler.js:405:31)
      at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
```

Co-authored-by: Jeremy Rifkin <51220084+jeremy-rifkin@users.noreply.github.com>

Author: xLuxy

src/command-handler.ts

@@ -134,6 +134,13 @@ export class CommandHandler {
         const command_name = match[1];
         if (!(command_name in this.text_commands)) {
             // unknown command
+
+            if (this.wheatley.devmode_enabled) {
+                await message.reply({
+                    content: `Unknown text command: ${command_name}`,
+                });
+            }
+
             return false;
         }
         let command_body = message.content.substring(match[0].length).trim();
@@ -186,7 +193,16 @@ export class CommandHandler {
 
     private async handle_slash_comand(interaction: Discord.ChatInputCommandInteraction) {
         if (!(interaction.commandName in this.text_commands)) {
-            // TODO: Unknown command
+            // unknown command
+
+            if (this.wheatley.devmode_enabled) {
+                await interaction.reply({
+                    content: `Unknown slash command: ${interaction.commandName}`,
+                    flags: Discord.MessageFlags.Ephemeral,
+                });
+            }
+
+            return;
         }
         let command = this.text_commands[interaction.commandName];
         let command_log_name = interaction.commandName;