feat: add Linq channel — real iMessage via API, no Mac required

Adds a complete Linq iMessage channel adapter that replaces the existing
iMessage channel's Mac Mini + dedicated Apple ID + SSH wrapper + Full Disk
Access setup with a single API key and phone number.

Core implementation (src/linq/):
- types.ts: Linq webhook event and message types
- accounts.ts: Multi-account resolution from config (env/file/inline token)
- send.ts: REST outbound via Linq Blue V3 API (messages, typing, reactions)
- probe.ts: Health check via GET /v3/phonenumbers
- monitor.ts: Webhook HTTP server with HMAC-SHA256 signature verification,
  replay protection, inbound debouncing, and full dispatch pipeline integration

Extension plugin (extensions/linq/):
- ChannelPlugin implementation with config, security, setup, outbound,
  gateway, and status adapters
- Supports direct and group chats, reactions, and media

Wiring:
- Channel registry, dock, config schema, plugin-sdk exports, and plugin
  runtime all updated to include the new linq channel

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/plugins/runtime/index.ts

@@ -92,6 +92,14 @@ import {
   sendMessageLine,
 } from "../../line/send.js";
 import { buildTemplateMessageFromPayload } from "../../line/template-messages.js";
+import {
+  listLinqAccountIds,
+  resolveDefaultLinqAccountId,
+  resolveLinqAccount,
+} from "../../linq/accounts.js";
+import { monitorLinqProvider } from "../../linq/monitor.js";
+import { probeLinq } from "../../linq/probe.js";
+import { sendMessageLinq } from "../../linq/send.js";
 import { getChildLogger } from "../../logging.js";
 import { normalizeLogLevel } from "../../logging/levels.js";
 import { convertMarkdownTables } from "../../markdown/tables.js";
@@ -378,6 +386,14 @@ export function createPluginRuntime(): PluginRuntime {
         probeIMessage,
         sendMessageIMessage,
       },
+      linq: {
+        sendMessageLinq,
+        probeLinq,
+        monitorLinqProvider,
+        listLinqAccountIds,
+        resolveDefaultLinqAccountId,
+        resolveLinqAccount,
+      },
       whatsapp: {
         getActiveWebListener,
         getWebAuthAgeMs,

src/plugins/runtime/types.ts

@@ -132,6 +132,15 @@ type SignalMessageActions =
 type MonitorIMessageProvider = typeof import("../../imessage/monitor.js").monitorIMessageProvider;
 type ProbeIMessage = typeof import("../../imessage/probe.js").probeIMessage;
 type SendMessageIMessage = typeof import("../../imessage/send.js").sendMessageIMessage;
+
+// Linq channel types
+type SendMessageLinq = typeof import("../../linq/send.js").sendMessageLinq;
+type ProbeLinq = typeof import("../../linq/probe.js").probeLinq;
+type MonitorLinqProvider = typeof import("../../linq/monitor.js").monitorLinqProvider;
+type ListLinqAccountIds = typeof import("../../linq/accounts.js").listLinqAccountIds;
+type ResolveDefaultLinqAccountId =
+  typeof import("../../linq/accounts.js").resolveDefaultLinqAccountId;
+type ResolveLinqAccount = typeof import("../../linq/accounts.js").resolveLinqAccount;
 type GetActiveWebListener = typeof import("../../web/active-listener.js").getActiveWebListener;
 type GetWebAuthAgeMs = typeof import("../../web/auth-store.js").getWebAuthAgeMs;
 type LogoutWeb = typeof import("../../web/auth-store.js").logoutWeb;
@@ -317,6 +326,14 @@ export type PluginRuntime = {
       probeIMessage: ProbeIMessage;
       sendMessageIMessage: SendMessageIMessage;
     };
+    linq: {
+      sendMessageLinq: SendMessageLinq;
+      probeLinq: ProbeLinq;
+      monitorLinqProvider: MonitorLinqProvider;
+      listLinqAccountIds: ListLinqAccountIds;
+      resolveDefaultLinqAccountId: ResolveDefaultLinqAccountId;
+      resolveLinqAccount: ResolveLinqAccount;
+    };
     whatsapp: {
       getActiveWebListener: GetActiveWebListener;
       getWebAuthAgeMs: GetWebAuthAgeMs;