feat: rewrite as moderation bot (#11)

## Summary

- Replaces the old AI companion bot with a full Discord moderation system
- Adds 8 slash commands: `warn`, `mute`, `unmute`, `kick`, `softban`, `ban`, `unban`, `prune`
- Adds logging for member join/leave, activity (messages, threads, voice), and moderation actions
- Audit log integration captures manual bans, kicks, timeouts, and unbans
- All applicable actions post sanctions to the Hikari sanction API
- All commands are ephemeral, use Components v2, and enforce permission + role hierarchy checks

## Test plan

- [ ] Run `pnpm register` to register all 8 commands to the guild
- [ ] Verify each command appears in Discord and is only visible to members with the appropriate permissions
- [ ] Test each command against a valid target and confirm mod log entry, DM notification, and sanction record
- [ ] Test each command against an invalid target (equal/higher role, self, bot) and confirm correct error response
- [ ] Perform a manual ban, kick, and timeout in the Discord UI and confirm audit log handler picks them up
- [ ] Perform a manual unban and confirm it logs correctly without creating a sanction
- [ ] Verify join/leave messages appear in the welcome log channel
- [ ] Verify message edits, deletes, thread events, and voice state changes appear in the activity log channel

✨ This issue was created with help from Hikari~ 🌸

Reviewed-on: #11
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src/commands/prune.ts

@@ -0,0 +1,125 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+/* eslint-disable max-lines-per-function -- Command handlers have many validation and action steps */
+
+import {
+  InteractionContextType,
+  PermissionFlagsBits,
+  SlashCommandBuilder,
+  type GuildTextBasedChannel,
+} from "discord.js";
+import { logModerationAction } from "../modules/logModAction.js";
+import { errorReply, successReply } from "../utils/components.js";
+import { logger } from "../utils/logger.js";
+import type { Command } from "../interfaces/command.js";
+
+/**
+ * Performs a bulk delete on a text channel and returns the number deleted,
+ * or null if the bulk delete fails.
+ * Wrapped to handle the type narrowing gap after isTextBased() checks.
+ * @param channel - The text channel to delete messages from.
+ * @param amount - The number of messages to delete.
+ * @returns The number of messages actually deleted, or null on failure.
+ */
+const bulkDeleteMessages = async(
+  channel: GuildTextBasedChannel,
+  amount: number,
+): Promise<number | null> => {
+  try {
+    const deleted = await channel.bulkDelete(amount, true);
+    return deleted.size;
+  } catch {
+    return null;
+  }
+};
+
+const pruneCommand: Command = {
+  data: new SlashCommandBuilder().
+    setName("prune").
+    setDescription("Delete the last N messages in this channel.").
+    setDefaultMemberPermissions(PermissionFlagsBits.ManageMessages).
+    setContexts([ InteractionContextType.Guild ]).
+    addIntegerOption((option) => {
+      return option.
+        setName("amount").
+        setDescription("Number of messages to delete (1–100).").
+        setRequired(true).
+        setMinValue(1).
+        setMaxValue(100);
+    }),
+
+  execute: async(interaction) => {
+    await interaction.deferReply({ ephemeral: true });
+
+    const hasPermission = interaction.memberPermissions?.has(
+      PermissionFlagsBits.ManageMessages,
+    );
+    if (hasPermission !== true) {
+      await interaction.editReply(
+        errorReply(
+          "Insufficient Permissions",
+          "You do not have permission to use this command.",
+        ),
+      );
+      return;
+    }
+
+    const amount = interaction.options.getInteger("amount", true);
+    const rawChannel = interaction.channel;
+
+    if (rawChannel?.isTextBased() !== true) {
+      await interaction.editReply(
+        errorReply(
+          "Invalid Channel",
+          "This command can only be used in text channels.",
+        ),
+      );
+      return;
+    }
+
+    const channelName = "name" in rawChannel
+      ? String(rawChannel.name)
+      : rawChannel.id;
+
+    /* eslint-disable-next-line @typescript-eslint/consistent-type-assertions -- rawChannel is narrowed by isTextBased() but the type union is not fully resolved */
+    const textChannel = rawChannel as GuildTextBasedChannel;
+
+    const deletedCount = await bulkDeleteMessages(textChannel, amount);
+
+    if (deletedCount === null) {
+      await interaction.editReply(
+        errorReply(
+          "Action Failed",
+          "Failed to delete messages. "
+          + "Messages older than 14 days cannot be bulk deleted.",
+        ),
+      );
+      return;
+    }
+
+    await logModerationAction(interaction.client, {
+      action:         "Messages Pruned",
+      emoji:          "🗑️",
+      moderatorTag:   interaction.user.username,
+      reason:         `Bulk delete of ${deletedCount.toString()} messages in <#${rawChannel.id}>`,
+      sanctionNumber: null,
+      source:         "Command",
+      targetId:       rawChannel.id,
+      targetTag:      `#${channelName}`,
+    });
+
+    await interaction.editReply(
+      successReply(
+        "Messages Pruned",
+        `Deleted **${deletedCount.toString()}** messages from <#${rawChannel.id}>.`,
+      ),
+    );
+  },
+};
+
+void logger.log("debug", "Prune command loaded.");
+
+export { pruneCommand };