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/line/http-registry.ts

@@ -0,0 +1,45 @@
+import type { IncomingMessage, ServerResponse } from "node:http";
+
+export type LineHttpRequestHandler = (
+  req: IncomingMessage,
+  res: ServerResponse,
+) => Promise<void> | void;
+
+type RegisterLineHttpHandlerArgs = {
+  path?: string | null;
+  handler: LineHttpRequestHandler;
+  log?: (message: string) => void;
+  accountId?: string;
+};
+
+const lineHttpRoutes = new Map<string, LineHttpRequestHandler>();
+
+export function normalizeLineWebhookPath(path?: string | null): string {
+  const trimmed = path?.trim();
+  if (!trimmed) return "/line/webhook";
+  return trimmed.startsWith("/") ? trimmed : `/${trimmed}`;
+}
+
+export function registerLineHttpHandler(params: RegisterLineHttpHandlerArgs): () => void {
+  const normalizedPath = normalizeLineWebhookPath(params.path);
+  if (lineHttpRoutes.has(normalizedPath)) {
+    const suffix = params.accountId ? ` for account "${params.accountId}"` : "";
+    params.log?.(`line: webhook path ${normalizedPath} already registered${suffix}`);
+    return () => {};
+  }
+  lineHttpRoutes.set(normalizedPath, params.handler);
+  return () => {
+    lineHttpRoutes.delete(normalizedPath);
+  };
+}
+
+export async function handleLineHttpRequest(
+  req: IncomingMessage,
+  res: ServerResponse,
+): Promise<boolean> {
+  const url = new URL(req.url ?? "/", "http://localhost");
+  const handler = lineHttpRoutes.get(url.pathname);
+  if (!handler) return false;
+  await handler(req, res);
+  return true;
+}