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/channels/dock.ts

@@ -18,6 +18,7 @@ import {
 } from "../config/group-policy.js";
 import { resolveDiscordAccount } from "../discord/accounts.js";
 import { resolveIMessageAccount } from "../imessage/accounts.js";
+import { resolveLinqAccount } from "../linq/accounts.js";
 import { requireActivePluginRegistry } from "../plugins/runtime.js";
 import { normalizeAccountId } from "../routing/session-key.js";
 import { resolveSignalAccount } from "../signal/accounts.js";
@@ -450,6 +451,23 @@ const DOCKS: Record<ChatChannelId, ChannelDock> = {
         buildDirectOrGroupThreadToolContext({ context, hasRepliedRef }),
     },
   },
+  linq: {
+    id: "linq",
+    capabilities: {
+      chatTypes: ["direct", "group"],
+      reactions: true,
+      media: true,
+    },
+    outbound: { textChunkLimit: 4000 },
+    config: {
+      resolveAllowFrom: ({ cfg, accountId }) =>
+        (resolveLinqAccount({ cfg, accountId }).config.allowFrom ?? []).map((entry) =>
+          String(entry),
+        ),
+      formatAllowFrom: ({ allowFrom }) =>
+        allowFrom.map((entry) => String(entry).trim()).filter(Boolean),
+    },
+  },
 };
 
 function buildDockFromPlugin(plugin: ChannelPlugin): ChannelDock {

src/channels/registry.ts

@@ -13,6 +13,7 @@ export const CHAT_CHANNEL_ORDER = [
   "slack",
   "signal",
   "imessage",
+  "linq",
 ] as const;
 
 export type ChatChannelId = (typeof CHAT_CHANNEL_ORDER)[number];
@@ -109,6 +110,16 @@ const CHAT_CHANNEL_META: Record<ChatChannelId, ChannelMeta> = {
     blurb: "this is still a work in progress.",
     systemImage: "message.fill",
   },
+  linq: {
+    id: "linq",
+    label: "Linq",
+    selectionLabel: "Linq (iMessage API)",
+    detailLabel: "Linq iMessage",
+    docsPath: "/channels/linq",
+    docsLabel: "linq",
+    blurb: "real iMessage blue bubbles via API — no Mac required. Get a token at linqapp.com.",
+    systemImage: "bubble.left.and.text.bubble.right",
+  },
 };
 
 export const CHAT_CHANNEL_ALIASES: Record<string, ChatChannelId> = {
@@ -116,6 +127,7 @@ export const CHAT_CHANNEL_ALIASES: Record<string, ChatChannelId> = {
   "internet-relay-chat": "irc",
   "google-chat": "googlechat",
   gchat: "googlechat",
+  "linq-imessage": "linq",
 };
 
 const normalizeChannelKey = (raw?: string | null): string | undefined => {