feat(signal): add poll support

Wire up signal-cli's sendPollCreate to the message tool, enabling
poll creation in Signal chats and groups.

- Add sendPollSignal() function in src/signal/send.ts
- Add sendPoll method to signal outbound adapter
- Support 2-12 options, single or multi-select

Closes #TBD

src/channels/plugins/outbound/signal.ts

@@ -1,5 +1,5 @@
 import { chunkText } from "../../../auto-reply/chunk.js";
-import { sendMessageSignal } from "../../../signal/send.js";
+import { sendMessageSignal, sendPollSignal } from "../../../signal/send.js";
 import { resolveChannelMediaMaxBytes } from "../media-limits.js";
 import type { ChannelOutboundAdapter } from "../types.js";
 
@@ -8,6 +8,7 @@ export const signalOutbound: ChannelOutboundAdapter = {
   chunker: chunkText,
   chunkerMode: "text",
   textChunkLimit: 4000,
+  pollMaxOptions: 12,
   sendText: async ({ cfg, to, text, accountId, deps }) => {
     const send = deps?.sendSignal ?? sendMessageSignal;
     const maxBytes = resolveChannelMediaMaxBytes({
@@ -37,4 +38,11 @@ export const signalOutbound: ChannelOutboundAdapter = {
     });
     return { channel: "signal", ...result };
   },
+  sendPoll: async ({ to, poll, accountId }) => {
+    const result = await sendPollSignal(to, poll.question, poll.options, {
+      multiSelect: (poll.maxSelections ?? 1) > 1,
+      accountId: accountId ?? undefined,
+    });
+    return { messageId: result.messageId };
+  },
 };

src/signal/send.ts

@@ -255,3 +255,69 @@ export async function sendReadReceiptSignal(
   });
   return true;
 }
+
+export type SignalPollOpts = SignalRpcOpts & {
+  /** Allow multiple selections (default: true) */
+  multiSelect?: boolean;
+};
+
+export type SignalPollResult = {
+  messageId: string;
+  timestamp?: number;
+};
+
+/**
+ * Create and send a poll to a Signal recipient or group.
+ */
+export async function sendPollSignal(
+  to: string,
+  question: string,
+  options: string[],
+  opts: SignalPollOpts = {},
+): Promise<SignalPollResult> {
+  if (!question?.trim()) {
+    throw new Error("Poll question is required");
+  }
+  if (!options || options.length < 2) {
+    throw new Error("Poll requires at least 2 options");
+  }
+  if (options.length > 12) {
+    throw new Error("Poll cannot have more than 12 options");
+  }
+
+  const { baseUrl, account } = resolveSignalRpcContext(opts);
+  const target = parseTarget(to);
+  const targetParams = buildTargetParams(target, {
+    recipient: true,
+    group: true,
+    username: true,
+  });
+  if (!targetParams) {
+    throw new Error("Signal poll recipient is required");
+  }
+
+  const params: Record<string, unknown> = {
+    question: question.trim(),
+    option: options.map((o) => o.trim()).filter(Boolean),
+    ...targetParams,
+  };
+
+  if (account) params.account = account;
+
+  // signal-cli uses --no-multi to disable multi-select, so we invert the logic
+  // Default is multi-select allowed (true), pass multiSelect: false to restrict to single choice
+  if (opts.multiSelect === false) {
+    params.multiSelect = false;
+  }
+
+  const result = await signalRpcRequest<{ timestamp?: number }>("sendPollCreate", params, {
+    baseUrl,
+    timeoutMs: opts.timeoutMs ?? 15_000, // polls may take longer
+  });
+
+  const timestamp = result?.timestamp;
+  return {
+    messageId: timestamp ? String(timestamp) : "unknown",
+    timestamp,
+  };
+}