feat: Add Line plugin (#1630)

* feat: add LINE plugin (#1630) (thanks @plum-dawg)

* feat: complete LINE plugin (#1630) (thanks @plum-dawg)

* chore: drop line plugin node_modules (#1630) (thanks @plum-dawg)

* test: mock /context report in commands test (#1630) (thanks @plum-dawg)

* test: limit macOS CI workers to avoid OOM (#1630) (thanks @plum-dawg)

* test: reduce macOS CI vitest workers (#1630) (thanks @plum-dawg)

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/plugins/http-registry.ts

@@ -0,0 +1,53 @@
+import type { IncomingMessage, ServerResponse } from "node:http";
+
+import type { PluginHttpRouteRegistration, PluginRegistry } from "./registry.js";
+import { requireActivePluginRegistry } from "./runtime.js";
+import { normalizePluginHttpPath } from "./http-path.js";
+
+export type PluginHttpRouteHandler = (
+  req: IncomingMessage,
+  res: ServerResponse,
+) => Promise<void> | void;
+
+export function registerPluginHttpRoute(params: {
+  path?: string | null;
+  fallbackPath?: string | null;
+  handler: PluginHttpRouteHandler;
+  pluginId?: string;
+  source?: string;
+  accountId?: string;
+  log?: (message: string) => void;
+  registry?: PluginRegistry;
+}): () => void {
+  const registry = params.registry ?? requireActivePluginRegistry();
+  const routes = registry.httpRoutes ?? [];
+  registry.httpRoutes = routes;
+
+  const normalizedPath = normalizePluginHttpPath(params.path, params.fallbackPath);
+  const suffix = params.accountId ? ` for account "${params.accountId}"` : "";
+  if (!normalizedPath) {
+    params.log?.(`plugin: webhook path missing${suffix}`);
+    return () => {};
+  }
+
+  if (routes.some((entry) => entry.path === normalizedPath)) {
+    const pluginHint = params.pluginId ? ` (${params.pluginId})` : "";
+    params.log?.(`plugin: webhook path ${normalizedPath} already registered${suffix}${pluginHint}`);
+    return () => {};
+  }
+
+  const entry: PluginHttpRouteRegistration = {
+    path: normalizedPath,
+    handler: params.handler,
+    pluginId: params.pluginId,
+    source: params.source,
+  };
+  routes.push(entry);
+
+  return () => {
+    const index = routes.indexOf(entry);
+    if (index >= 0) {
+      routes.splice(index, 1);
+    }
+  };
+}