TypeScript: add extensions to tsconfig and fix type errors (#12781)

* TypeScript: add extensions to tsconfig and fix type errors

- Add extensions/**/* to tsconfig.json includes
- Export ProviderAuthResult, AnyAgentTool from plugin-sdk
- Fix optional chaining for messageActions across channels
- Add missing type imports (MSTeamsConfig, GroupPolicy, etc.)
- Add type annotations for provider auth handlers
- Fix undici/fetch type compatibility in zalo proxy
- Correct ChannelAccountSnapshot property usage
- Add type casts for tool registrations
- Extract usage view styles and types to separate files

* TypeScript: fix optional debug calls and handleAction guards

extensions/twitch/src/actions.ts

@@ -15,7 +15,7 @@ function errorResponse(error: string) {
   return {
     content: [
       {
-        type: "text",
+        type: "text" as const,
         text: JSON.stringify({ ok: false, error }),
       },
     ],
@@ -120,11 +120,12 @@ export const twitchMessageActions: ChannelMessageActionAdapter = {
    *   accountId: "default",
    * });
    */
-  handleAction: async (
-    ctx: ChannelMessageActionContext,
-  ): Promise<{ content: Array<{ type: string; text: string }> } | null> => {
+  handleAction: async (ctx: ChannelMessageActionContext) => {
     if (ctx.action !== "send") {
-      return null;
+      return {
+        content: [{ type: "text" as const, text: "Unsupported action" }],
+        details: { ok: false, error: "Unsupported action" },
+      };
     }
 
     const message = readStringParam(ctx.params, "message", { required: true });
@@ -159,7 +160,7 @@ export const twitchMessageActions: ChannelMessageActionAdapter = {
       return {
         content: [
           {
-            type: "text",
+            type: "text" as const,
             text: JSON.stringify(result),
           },
         ],