refactor(plugin): extract channel/decision parsing modules and unify channelId resolution

plugin/decision-input.ts

@@ -0,0 +1,37 @@
+import {
+  extractDiscordChannelId,
+  extractDiscordChannelIdFromConversationMetadata,
+  extractDiscordChannelIdFromSessionKey,
+  extractUntrustedConversationInfo,
+} from "./channel-resolver.js";
+
+export type DerivedDecisionInput = {
+  channel: string;
+  channelId?: string;
+  senderId?: string;
+  content: string;
+  conv: Record<string, unknown>;
+};
+
+export function deriveDecisionInputFromPrompt(params: {
+  prompt: string;
+  messageProvider?: string;
+  sessionKey?: string;
+  ctx?: Record<string, unknown>;
+  event?: Record<string, unknown>;
+}): DerivedDecisionInput {
+  const { prompt, messageProvider, sessionKey, ctx, event } = params;
+  const conv = extractUntrustedConversationInfo(prompt) || {};
+  const channel = (messageProvider || "").toLowerCase();
+
+  let channelId = extractDiscordChannelId(ctx || {}, event);
+  if (!channelId) channelId = extractDiscordChannelIdFromSessionKey(sessionKey);
+  if (!channelId) channelId = extractDiscordChannelIdFromConversationMetadata(conv);
+
+  const senderId =
+    (typeof conv.sender_id === "string" && conv.sender_id) ||
+    (typeof conv.sender === "string" && conv.sender) ||
+    undefined;
+
+  return { channel, channelId, senderId, content: prompt, conv };
+}